Placeholders - bit stuck

Please forgive a slightly off-topic question regarding:

I occasionally see the “| … |” notation in DT AppleScripts but I don’t entirely understand it. As you might imagine, results of web searches for “applescript |” aren’t too helpful.

Other than “vertical bar” or “pipe,” what is the “|” operator called in this scenario, and what is the sequence “| … |” called?

In this script, the purpose seems to reference the occurrence of the string literal “%recordName%” in the contents of templateFile, but I have seen it in other contexts that extract data from an item’s metadata, as in:

set theSubject to |kMDItemSubject| of theMD

In the post:

In this scenario, are “|” and “| … |” called the same thing as in the “|%recordName%|” scenario?

It seems that the target of these constructs is text/string. Are there other uses of these constructs?

Many thanks.