I heart chain piecing

To chain piece is to sew sets (usually of 2*) of fabric together one set after another, without cutting the thread in between sets.
Chain piecing is a fast way to sew a bunch of pieces of fabric together quickly, especially if you're sewing hundred(s) of little squares or triangles together (BTDT).
Chain piecing is great because it wastes less thread, and keeps the needle from unthreading if the take-up lever isn't all the way up when you last stopped sewing.
It is super-annoying and a massive time waster to have to stop to rethread your needle and/or fish the bobbin thread out of the bobbin case. It's the same as using a starter scrap to keep your thread ends from getting sucked away, only you're not using a starter scrap. It's the same, but different! LOL
*I know of one exception: you sew 3 pieces together at once for Kaye Wood's Attic Windows pattern