Every public figure needs to be comfortable speaking in different situations.
There are three basic types of situations:
1) Impromptu
You're at a meeting and somebody asks you to say a few words. You walk outside and get surprised by a TV reporter with a microphone and film crew. Or you're on a panel and get asked a question you hadn't prepared for at all.
Impromptu speaking is speaking without any notes or preparation. It's the equivalent of improv theater.
2) Extemporaneous
This is speaking with a little time to prepare -- maybe five minutes or half an hour. Enough time to write a few notes on an index card or legal pad.
Or it's a situation where you don't know exactly what you'll be asked to say: a press conference, a forum or a panel. This is a situation where talking points are often useful.
3) Full text
A longer speech on a known topic for a known length. The good news? No surprises. The bad news? Higher expectations.
It takes practice to get comfortable reading page after page of text without LOOKING like you're reading text -- or to read from a teleprompter.