A serger uses 3, 4, or 5 threads to sew a seam, trim off the raw edges, and finish the edges all at the same time. It uses loopers fed by multiple thread cones rather than a bobbin. Loopers serve to create thread loops that pass from the needle thread to the edges of the fabric so that the edges of the fabric are contained within the seam.
The Juki MO-735 is a 2-Needle, 2/3/4/5-Thread Overlock + Cover Stitch Sewing Machine. As the name implies, it can sew a variety of different types of stitches: overlock stitch, cover stitch, flatlock stitch, and rolled hem.