Usually they will include information to help the receiver identify the sender, place of work, phone numbers and so on. You have complete editorial control over the appearance and content of these signatures. Many people seem to spend their entire working life designing a signature that uniquely identifies their soul.
Spaces usually work better than tabs for clear layout.
The first two signatures are more important than the third. To play safe, the thing to do is to create the same signature for all three options and then it will not go wrong, but then you might not want a signature on local messages. To add fog to this situation, you can now have up to nine different signatures for sending to different types of recipients of your mail. You could have a formal one for funders, an informal one for collaborators around the globe, and a humorous one for friends, and so on. You should always start your signature with a few blank lines so that there will be a natural gap between the message and the signature at the bottom.