In the Member Manager, there are a few member statuses:
Active - An active member
Banned - A banned member
Draft - Someone who has signed up but not clicked the below 'Next Step' button, and also not clicked the link in the verification e-mail.
There is also 2 other status', that are not in that drop down, but that do appear in the Member Manager above it:
Email Pending - This shows when someone has signed up and has clicked the above 'Next Step' button, but not clicked the link in the verification e-mail, for example if signing up with Twitter.
Need Approval - This shows when you have turned member approval on. You will need to click on the 'need approval' link when a new member joins, then you will be taken to a page that lets you 'approve' or 'delete' the new member.