“WHY use the terms ‘bourgeois’ and ‘proletariat’? Most people don’t know what they mean.”

You’re probably right. And in answer to your question; we probably shouldn’t, except in a historical context.

In a footnote to the 1883 edition of The Communist Manifesto, Engels wrote: “By bourgeoisie is meant the class of modern capitalists, owners of the means of social production and employers of wage labour.

By proletariat, the class of modern wage labourers who, having no means of production of their own, are reduced to selling their labour power in order to live.”

That’s probably the most succinct definition you’ll find anywhere.  
But both the ruling class (capitalists and their political representatives) and the working class (those who have little or no capital, who have to work to live and to support their families) have changed since the days of Marx and Engels.  

A working class exists in all class societies, including slavery and feudalism. Marx borrowed the term “proletariat” from the French who took it from Latin. (In ancient Rome “proletarius” applied to the lowest class, who were compelled to work, or die.)  

Marx gave the name proletariat to the new working class that emerged with industrial capitalism, composed mainly of manual workers (“wage labourers”) who survived by selling the only thing they had to sell — their labour power.  

He saw the proletariat as potentially revolutionary because their employment conditions brought them together in the workplace and in communities and they were central to the dynamics of capitalism.  

This was in contrast to other workers, including the peasantry (still widespread in Europe though largely abolished in Britain) as well as small shopkeepers, independent craftspeople and other “petite bourgeoisie” whom Marx considered largely conservative.  

Today the working class is no longer composed primarily of manual workers in industry and agriculture.  

In Britain the majority of employees work in the service sector: in shops, transport, utilities, or in “white-collar” clerical, professional or administrative jobs.  

Public employees, health workers, teachers, scientists, small traders, the self-employed — all have to work for a living and all are to a greater or lesser degree exploited; they produce (directly or indirectly) more value than they receive.  

Everyone who works for a living (who sells their labour power) together with their families and dependants, including those unable to work through ill-health or disability, constitute “the many” — the working class.  

The ruling class has changed, too. “Bourgeoisie” originally meant the freemen (including merchants and craftsmen) of French towns (equivalent to the German bürgers) of the Middle Ages. 

In France this class abolished aristocratic privilege and became politically dominant in the late 18th century, following the collapse of the “ancien regime” (of the royal family, nobles, and the Catholic church) in the revolution.  

Marx extended the term to the new ruling class — factory owners and their political representatives — of industrial capitalism.  

Today most industrial, commercial and financial capital is no longer owned directly by individuals. Instead it is held through companies, whose shares and stocks are increasingly held via global financial institutions — banks, hedge funds, private equity firms etc, who also increasingly also own land (rural and urban) and buildings.  

The link between the richest individual investors and the point of creation of profit is usually mediated through chains of companies and the processes of “production, distribution and exchange” are directed by managers.  

But the control as well as the ownership of capital is still overwhelmingly in the hands of a tiny number of individuals.  
The terms bourgeois, petite (or “petty”) bourgeois and proletarian are today rarely employed in serious economic or social analysis.  

They are still sometimes used in left-wing circles, usually imprecisely, with primarily cultural connotations and often in a derogatory way.  

“Bourgeois” is used to denote affluence, lifestyle, aspirations or values seen as characteristic of the “upper” strata of society, while “prole” is sometimes applied contemptuously to manual workers and their supposed “working-class” outlook and habits. Neither term is particularly helpful today.  

Marx also used the dismissive term “lumpenproletariat” (“lumpen” meaning “slouch” or “rag”) to describe those on the margins of society, unemployed or surviving through casual or occasional work, including petty criminals and beggars who (he argued) took no part in socially useful production, generally lacked political consciousness and were lost to class struggle.  

Others such as the anarchist Mikhail Bakunin (Marx’s contemporary) and, later, anti-imperialists such as Frantz Fanon, and Black Power activists such as Huey Newton, argued that “the wretched of the Earth,” the “great masses of the poor and exploited” had a spontaneously revolutionary potential but could also be co-opted by counter-revolutionary forces. The “dispossessed masses” should therefore be central to revolutionary strategy.  

And some ultra-left groups claim that colonial and neocolonial exploitation of the Third World means that either the whole working class or at least sections of it in the imperialist core economies like Britain have become “embourgeoisified” (and lost to the struggle for socialism).  

But experience over recent decades shows that this is clearly not the case.  

In today’s “gig economy” the increasing numbers of people in precarious, temporary or occasional work, including the self-employed, are most definitely members of the working class.  

And the “proletarianisation” of what even today are sometimes considered “middle-class” occupations — from scientific research, to medicine or teaching — is a feature of modern capitalism.  

Teachers, nurses, scientists — all today work mainly as employees (or dependant self-employed workers) and they all contribute to surplus value, directly or indirectly.  

They are objectively part of the working class and have the same potential as other workers to understand and act collectively to overthrow the undemocratic rule of the tiny number of individuals who exercise real power. 

So it is important to see all these terms in an historical context, and to use them (if at all) as a focus for analysis of dynamics of class and capital in relation to the particular conditions in specific periods and places.  

And in all debates around class and class consciousness it is important to emphasise that all workers have a common interest to struggle against capitalist exploitation and power.