The steem icon indicates that particulate post is powerupd by 100%. That means that someone has voted on post with 100% of their voting power.

Hope this helps :
Visit my blog at https://steemit.com/@pritpatel
to get the basic ideas about things like this please view my post.
https://steemit.com/steemit/@pritpatel/the-hitchhiker-s-guide-to-steemit.

Please do upvote, follow and steem on :-)