Blocking someone on Twitter makes the blocked account unable to see your tweets, message you, or follow you. If you cannot see the users’ tweets, if you cannot message to this user or if you cannot follow this user anymore, this means that this Twitter user has blocked you. In addition, it means that you cannot do all these things until this user unblocks you. This Twitter user that has blocked you will also not be able to see your account. He or she will not be able to message you, see your tweets or follow you.