I actually had not heard the term outside of a writing/screenwriting context-- Enlightening XD

That said, David Mandel (Veep) gives us a good definition:

“‘Laying pipe’ is sort of laying down the narrative stuff that you need in a script that's going to … come back later. It's like, I've got to make sure early on that you know this guy has a sister who he is estranged from, so that sister can come back at the end of Act One. That's laying pipe. I'm going to figure out a way — in my scene where I'm talking to the grocer, the grocer is going to say, 'Do you want raspberry jam?' And I'll go ‘Oh, no. You know, my sister who I never talk to is allergic to that.’ And so it seems like a very natural thing, but I'm laying the pipe so that later on, she can show up and you know she exists, and the plumbing all works.”

(https://www.pri.org/stories/2017-04-18/how-talk-tv-writer-explained-david-mandel-veep)

Essentially, it's what prevents events that happen later in a film or story from feeling like they pop up out of the blue. To me, making sure to lay pipe can help a story feel more cohesive.

Glad my take didn't disappoint!