Your reputation level is where you stand within the community, and the higher the better. Your current reputation is displayed on the Home Tab as shown below.
You can see both a large number and a progress bar, The number on your left is your current reputation level and the progress bar allows you to track your progressive to your next level.
The reputation system was originally designed to be a tool to aid Support, as well as safeguarding users and protecting groups from spammers. But only a small amount of users were able to benefit from such protection, and so the decision was made to make Reputation visible.
Our goal is to give you, our valuable users, the best possible experience, by providing you with a strong, stable platform, with quality content, interesting people, and engaging discussion. Or, to put it another way, just a great place to hang out with your mates.
Group Owners and Admins can use Reputation to set an entry requirement for their groups, giving you greater control of your Group. You can set this here or in your app as explained in the How to create a group FAQ.