I came across a user account that appears to have been suspended for at least a few days, yet was "last seen" 6 hours ago. On other websites (outside the Stack Exchange network) being suspended can mean totally unable to log in and access the site. What does being blocked on SE do? Can the user log in and view the site, and is just unable to post (and anything that requires >1 reputation point)?
Suspension allows login and reading. It disallows posting, commenting, editing (including one's profile; h/t Monica Cellio), suggesting an edit, accepting an answer, voting (including voting to close/delete), flagging, reviewing, and offering/awarding a bounty. But the suspended user can reply to the site moderators (who message him when suspending; h/t DoubleAA) and can communicate with Stack Exchange employees via the contact link. More details.