No problem with the questions at all, Mint - good thing to ask if unsure. I'll answer things one by one:
What do you define as from scratch?
From nothing.
Is it just what you drew?
Yes - your own work from a blank sheet of paper (or blank screen) or a photograph you personally took (but not a photograph of a photograph).
Is it if you scanned pick from a book and made an avatar out of it?
No.
Is it that you took a pick of smth and cut a part of it to make it an avatar?
No (unless by "took a pick of smth" you mean you were the person who photographed the thing (for example if you photographed your pet hamster, that photo (or part of it) is fine - AND bear in mind
you are the copyright holder of that photo, so you can allow others to use it if you wish BUT if you don't specifically state that others can use it, then if they do use it, they infringe upon
your copyright (so you see, copyright protects everyone)).
Reason why it applies to this forum?
It applies everywhere.
Other forums seem to be using them without any trouble?
Some forums or sites are run by people who flout the rules, don't know or don't seem to care. Copyright infringement can and does get sites closed down. I'm not going to allow that to happen to BAO. If my determination to keep the forum (and myself) safe from copyright infringement problems annoys some people, I'm sorry, but it's to ensure the long-term life of this site.