What's the difference between Pending and Blocked

When you want to kickout an existing user then you Block the user. But when you have a new user asking for access to your community you see Pending status.

There are probably different info displayed to the end user for those options.

I am not aware if there are any other difference but maybe we will see more details in docs soon.

Technically both are the same in terms of access to the portal. We kept the pending status for future use where you can take the membership application and then approve it.