The VHL is basically a third party league created by users that uses lobbies to run 6 vs 6 games in an organized fashion. There's a website, teams, rosters, trades, etc... everything you'd expect to find in a real league. It's just all organized off site, since EA doesn't enable any in game league management.
It's just one of many leagues out there (the largest, but also arguably the least "team play" oriented). Honestly these 3rd party leagues are one of the only reasons I still play this game. Each league is different and has its own goals and reasons for being created (and in turn, attracts its own style of players), but when you find the right type of league, there's nothing else like it in online sports gaming imo... Playing club is fun, but the incentive to care just isn't there. The whole amateur, pro, and elite playoffs thing once a month is played out after so many years and really is outdated. These leagues fill the void and give people something to play for, the same as any other online league for other sports games (except this is for 6 vs 6 play, rather than regular versus).