Is there a way I can auto fill a text area based on a selectbox drop down?

I'm trying to auto fill a textarea based on the selection of a selectbox.

I want the auto fill text to come from my database and it would be nice if the option names in the selectbox could come from the database also, but not necessary - they can be static.

I'm sure I will have to use some kind of JavaScript or Json, etc. Any help you can give I appreciate it.