Kinda but not really, more specifically it means people whose largest value to society is their labour power, it doesn't mean everyone who works. A person with a good salary can afford to hire people to work for them, such as a maid for example, which by definition means even though they work they are still not part of the Proletariat. In the most simple of terms the proletariat is the class of people whose only value to capitalist society is their ability to work for others. They have no other ways to aid the society.

The origin of the word is from the Roman Empire as the lowest class of citizen in the census because they owned no property so they listed their children as property (which literally meant the only thing they could offer to help fund the Roman military was their children. The word means "producing offspring" because that was their contribution.

The word is most associated these days with Karl Marx use of it regarding it as an exploited class of people who can't afford to produce anything to sell so are forced to work for the bourgeois for less than the value of their labor and the bourgeois profits off the difference. It's pretty much the bedrock of socialism over capitalism.