Most have to deal with dialing numbers.
Lets say you dial your voice mail, you can put a pause in there (so the service can say it's stuff)then you put in your password. This way you don't have to sit there and listen to all that garbage they say every time.
Same goes for instance if you call your home number and need a pause because of the speech you set up before you can dial in your password.
That is what they are used for.