Who are the proles and what is their importance to the story in 1984?

Proles are neither members of the Inner Party nor Outer Party and enjoy relative
freedom compared to those likewho are under constant surveillance. However, they are also kept
poor and ignorant and do not truly understand their own oppression. One of the Party's slogans
captures their place in society quite well: "Proles and animals are free." Thus, the
Party equates this group constituting around 85% of the population to having the worth of
animals in this society. The proles are not generally required to keep telescreens in their
homes. They are allowed liberal sexual freedom. They enjoy football and beer and fight with
their neighbors. And they aspire for little else.

The Party also uses them as
minions to keep proper surveillance on the happenings of society and to root out any signs of
traitors. Consider this comment from book 1, chapter 5:

That's a first-rate training they give them in the Spies nowadays €“ better than in my day,
even. What d'you think's the latest...