What happens when you paste an app into TextEdit? In the past, I have pasted apps into TextEdit, which would show something like the following. I always thought that this was a convenient way to store app icons (as .icns files), in case I ever wanted to back a list of my apps up (just the names/icons, not the apps themselves) to manually download and install later.
I recently tried pasting about 20 apps into a TextEdit document, and the document turned out to be about 3GB large. This definitely is much larger than the .icns files for 20 apps. What exactly is stored in this TextEdit document?
When pasting an application into TextEdit as an RTF document and saved as Rich Text Document with Attachments it creates a Rich Text document bundle, e.g. Untitled.rtfd and will contain a copy of the application pasted into the document.
The more apps you paste into the document the larger it will be.
You can check the contents of the e.g. Untitled.rtfd document bundle by selecting it in Finder and right-click then select Show Package Contents.
There you will see a copy of each application bundle you've pasted into the Rich Text Document that was saved as Rich Text Document with Attachments.