:salamext: brother greenhill,
I hope you are finding the forum beneficial. Be careful of not allowing it to consume too much time!
At the bottom of each post, there is a button which allows you to give feedback on others' posts (if you hover above it, it says
'Add to this user's reputation'). A pop-up will then appear where you can give the post positive or negative reputation, and also submit some feedback on the post. So the user will receive a feedback comment (which is optional), and they will automatically receive some points known as reputation points. So on the user panel, 'reputation' is how many reputation points you've received from others.
How many points are given depends on something called 'reputation power'. Each person's reputation power depends on a few factors, such as how long a person has been registered for, how many posts they have and how many reputation points they have received.
I hope this has made sense :ia:.
About avatars, you cannot upload your own avatar until 50 posts. I can't remember if you can choose a custom one in the meantime. To check if you can, go to Settings at the top right, then edit avatar. Here's a list of things you can't do whilst a limited member:
http://www.islamicboard.com/faq.php?faq=get_started#faq_limited_mem_ber