Once you've created a profile and updated it in any way you like, you may want to add a Contribution to the site. These Contributions are tabs, reviews, news, lessons, articles and TV (although most people will never use this one).
Tabs are the depictions of how a song should be played. There are many sections and sub-sections of the Tabs section. There's the tablature section, and chords, bass and drums sections. And then even deeper inside of these, you get intros and solos. Some determined Users even submit an Album Contribution in which you tab out every song in an album, all under a single tab submission. You can also submit video lessons and Tab Pro lessons (which if I'm mot mistaken requires a paid subscription). There is a large chance that if you submit a tab that has been done to death, it won't be accepted.
Reviews are sort of self-explanatory: you review a CD, DVD, concert, equipment, games etc. If you submit a review of an item that has already been done, it will be added to the same page as all others so that all reviews will be together on one page.
News is also really simple to understand. Providing that it is music-related - although, occasionally, miscellaneous subjects will be allowed. Basically you are regurgitating music news that you have heard or read elsewhere and added it onto the site.
Lessons have a very wide scope. You can teach viewers anything music-related. How to play a guitar, equipment lessons, recording lessons, songwriting lessons etc.
Articles can be about almost anything. You can make one about any subject you want. You can write a How To guide, write a fictional series, write Lessons - such as this one - that wouldn't fit into the Lessons section. Do just about anything, it becomes addictive after a while. The downside to Articles is that - aside from News contributions - this is the section that Users are most vocal about and most will not hesitate to give their own opinions, wanted or otherwise.
Regarding the TV section, your guess is as good as mine. Not only have I never submitted one, but I've never seen a User that has. If you have or you've seen a profile that has, please write a reply in the Comments and enlighten us all.
If your Lesson is well-written and relevant, you have a good chance of having your submission accepted. Although some Contributions are more difficult to get accepted than others. Tabs are relatively easy, especially if it's under the Misc Unsigned Bands section and it hasn't been submitted many times before. Reviews are also relatively easy to get accepted. Articles are possibly the easiest to get accepted (I personally have more or less 12 articles, all of with were accepted the first time). Lessons are also quite easy to get accepted. The only difficult submission is News. There is a good chance that if you chose the wrong story, or if you didn't write it as well as you could have, then it will be denied.
Moving on to your fellow UG'ers. You have a mixture of people here. Many are mature, but there is a fair number of people who Comment the first thing that comes to their minds.
There are a few things that you can do to keep your head from getting bitten off by other Members. First of all, stay away from Articles unless you have considerable writing skill. Also, if it is focused on something completely subjective, such as your favourite band, people will not hesitate to give their own opinion. This also tends to happen in Reviews if you don't do them well. If you Comment without thinking, or if you make a biased Contribution, you can expect a lot of low-rated submissions and many Comments.
I'll post more Articles soon, and don't forget to post a Comment if you know anything about TV contributions. Maybe post a link to the page.