Should be self explanatory. I was thing something like the ones used at this forum
If you mean the category, e.g. staff, it's possible if you create a custom homepage.
To do this on the Wix Forum, you wouldn't be able to have the categories display the title and the most recent post of each category on the homepage. You'd need to create custom forum homepage to replicate this.
However, if you just want to show posts with a slight category display, you can make it look like this (I've just hidden some details like author name, post title):
The categories will display next to the posts if you have the homepage set to "list of posts".