Blocked users are users who are unable to edit pages, upload files, move pages, create pages, and perform other actions that additional user rights would grant. Administrators or others with access to the blocking and unblocking interface may not block nor unblock others (except themselves) while blocked.
Blocked users can still view and edit their watchlists. Depending on the settings implemented on a block where specifically disallowed, users can typically edit their own user talk page and/or send e-mails using Special:EmailUser (registered accounts only).
Administrators and Stewards can block users (unregistered or logged in). Global sysops can also block users on wikis opted in to the global sysop wikiset. Administrators or others with access to the blocking and unblocking interface may, may not, be able to block or unblock others or themselves while blocked, depending on the configuration of the wiki.