If you copy something, it goes to a virtual clipboard on the iPad. The only way to access it is if you opened an app and, after pressing the screen to get the option, pasted the copied data in the app.
It's like a computer in that the virtual clipboard is "erased" every time you copy somet NGO; the new copy command will overwrite whatever was there. However, it's a bit different in that if you copy something and try to past it into an app that doesn't handle that type of file/input, it won't work. For example, if you copy a photo and then try to paste it into your Notes app, it won't work as the Notes app is text only.
Hope this helps.
Marilyn