The Internet has given us a new symbol in our lexicon: The "like".
Not to be confused with "thumb war".
It is a staple of the Facebook experience. If you see content on Facebook that instills positive emotion in you, then the provided way to express that emotion is to hit the 'like' button. It streamlines the entire response process - you get to state your approval of something and everyone else gets to know it.
The symbol has since evolved to take on independent functions in online context. 'Liking' things on Facebook moves them up higher in the home feed, exposing it to more viewers. 'Like's on YouTube function as ratings, with high-liked content being recommended more often to other YouTube users.
Reddit's upvote/downvote system functions similarly to this, where users can vote content up and down if they personally approve of it. What's more, sometimes people on Reddit will physically post 'upvoted' or 'downvoted', so as to communicate their approval (or lack thereof). On bodybuilding.com, approval of individual users can be expressed by voting to increase their reputation, or 'repping' them. Just as in Reddit, people will often respond to things with 'repped' in order to make their approval known. On 4chan, posting 'sage' functions in a way so that the thread doesn't get brought up to the top of the page, and is used to express disapproval of a thread's content in the same way that saying you 'downvoted' something does.
This is the new language of the online. Abstract concepts and functions are becoming recognizable and commonplace terms.