What is Steem actually?

Steem is a cryptocurrency that allows people to earn rewards for their contributions to the Steemit community. Rewards are given out in the form of Steem Power, which can be used to upvote content and give other people more exposure. The more Steem Power you have, the more influence you have on the site.

We also can say about Steem in a different way -

Steem is a decentralized social media platform that runs on blockchain technology. This means that there is no central authority controlling the platform. Instead, it is run by the community of users who contribute content and upvote or downvote each other's posts.