Avatar is like a profile image in your account and you can using it to earn more cryptocoin by joining a bounty campaign. Maybe if this wrong, a senior can correcting it.
It depends,just as it does when it relates to signature also...
There are two types of signture/avatar..
There's the personal one(based on your preference and what you'll like to display),then there's the one for bounty programs(were you're expected to put it on inorder to advertise for them)
So it varies,if you're a full member and above on a bounty that requires you to put on an avatar,you'll wear the specific avatar of the project,and thus advertise for them(and make money as you said)
But if you're not on any bounty as a full member and above,its up to you to put up an avatar of your choice(its optional)
Same thing also applies to a signature,only the restrictions are less, as Jr member and above are allowed to wear either a bounty signature or their personal signature..
