For FMQ, most quilters use a "hopping" foot that has a spring in it. The foot holds the fabric down while the stitch is being formed, but hops back up in-between stitches so you can move the quilt. There is another type of FMQ foot that doesn't hop, but I've never used that one. As others have said, that one keeps a minimal amount of continual pressure on the sandwich to stop it from popping up when the needle moves up. These feet are usually not expensive at all. Most sewing machines have either a short shank or long shank, and a generic darning foot of the correct shank type is all that is needed.
Oh, and it's not a stupid question at all! The only stupid question is the one that doesn't get asked.
