An asset is a file that a page points at. The name of the asset is the address, and the address is why an old page can still be read.
About 1 min of reading
Name an asset with a version
Write the versioned name
Before you run it, say out loud what it will print. Then open the answer.
Answer a request
Before you run it, say out loud what it will print. Then open the answer.
Keep an old name
Before you run it, say out loud what it will print. Then open the answer.
A name that changes is a name a reader cannot trust. A version in the name is a name that cannot change.
A page that points at a name that was not built. The pair is the answer, and the answer names both.
The name carries the version. A name that carries a version is a name that never changes.
The page asks for a name and the build answers with a name. The answer is the pair, and the pair is what is compared.
Kept, not replaced. Kept is what makes a page that was cached still render.
Each one is defined here on this site. Open the entry for the full definition and the other words it points at.