I think the word you are looking for is clipboard (or similar).
On a phone, when you select a piece of text you usually get an option to copy it (or cut when possible) to the clipboard, so that you can paste it, or some of it, somewhere else. Similar to how it is working on a computer you usually do not access the clipboard, you just use it achieve something. (In fact, I think they removed the clipboard manager (software) from Windows Vista or 7, and later on; something similar can be installed as a third-party software or app.)
And in the phone case once you copy new data the old one is lost, it's in memory as long as it isn't replaced.
The immediate question is: what are you trying to do, without going into details about what you are trying to copy. And what have you tried? Have you started an app and tried to paste the copied text?
It seems you either need a text editor to save your notes, copies of text etc. and there are plenty of apps for that, or looking for some clipboard manager software such as Clipper.
See, for example, these threads (there are plenty of them out there):
https://forums.androidcentral.com/sprint-photon/111649-text-has-been-copied-clipboard-where-clipboar...
https://www.wikihow.com/Access-the-Clipboard-on-Android
