1. Repost popular content on Reddit, 4chan
2. Spam the shit out of social links
3. ...?
4. Profit
actually they manage to build their own community around it. there was even 'war' 9gag vs 4chan sometime ago and surprisingly their members were able to defend against 4chan spam and even counter attack.
from
As far as I can ascertain, it's an aggregator for funny pictures found on reddit.