I've never heard anyone just call it "Pipe in Pipe" in industry, but okay.
One of the main things you need to look at are elbows or changes in direction. For example, while a 4" straight pipe fits nicely inside a 6" straight pipe, a 4" 90 does not fit inside a 6" 90.
If you're trying to provide secondary containment for a large OD pipe, double wall piping probably isn't the most cost effective solution.