Sewing machines don't sew, so much as they loop threads around each other. Essentially, it pushes the thread on the needle through the fabric. While the needle is pushed through, the thread on that needle is looped around a second thread on the bottom, and then pulled back up. This process repeats. If you were to remove the bottom thread, the all the stitching comes apart.

I'm not sure I would say Singer is the best, but they're the most recognized brand for sure.