Official Reddit Page!

[yottabyte]

Reddit is known as "the front page of the internet". People submit links to various things such as viral videos, news, pictures they've taken of stuff and if the Reddit community likes the link, they can upvote it. If they don't like it, they downvote it. This way, if you go to the front page of Reddit you will see things that people generally like and want others to see.
It's also made up of subreddits, so you can choose to subscribe to certain links. Examples are r/gaming for computer games, r/Minecraft for all your Minecraft fun stuff or r/worldnews for general news.
People can also comment on any link and upvote/downvote these comments. This can start pretty interesting discussions but usually it's just puns and jokes.
Every time someone upvotes a link or comment you've made, you get karma points. These don't do anything, but the human mind always wants to be better than everyone else, so people naturally want more karma, which often turns into spending hours upon hours on the site.
There's also this thing known as the "Reddit hivemind", which essentially describes what the average Redditor likes, based on what makes it to the front page. The hivemind dislikes the US government, EA, gaming consoles, Minecraft pixelart. It likes Valve, Scandinavia, PC gaming and piracy news.
Of course, this also leads to good things. The Reddit community was a big part of the whole anti SOPA/PIPA movement, for example.

SirSuba made a Kiwike subreddit, that you can subscribe to and see Kiwike related links on your reddit frontpage.

tl;dr: It's a terrible site, when you start going there regularly it turns into an addiction. Don't go there.