Levelling is simple, stay active, participate in the community and you will level-up based on the quality of content contributed and your time online. For example if you add a game and a development tutorial you will gain activity points (vice-versa is also true - spam the comments, forums or news and you will lose AP). Each day based on how many points you have earnt, your current level will be recalculated and your % complete towards the next level will be shown.
Level names are either a special title, mod, indie game, headline or something related to the site. Each headline has a meaning of some relation to the site, be it small or huge. Their order is not necessarily significant.