Sergers have two loopers, whereas coverstitch machines only have one. A serger machine always includes two cutting knives that trim uneven fabric edges while you stitch, resulting in an even working area, but a coverstitch machine doesn't. Coverstitch machines are generally used to make garment hems seem professional. It serves the dual purpose of concealing a fabric's rough edges while also preserving the fabric's stretchability. Also, If you have access to or possess a serger, it may be incredibly helpful in the hemming procedure. Sergers provide a neatly hemmed edge in just one step, making them faster than most conventional hems.
Sergers also have a blade that cuts the fabric as the machine stitches, so the thread can loop around the edge in a neat way. Sergers aren't necessary, but they're great for finishing seams quickly. They are also great if you sew a lot of knits because the way the stitch is made makes it stretchy by nature. Sergers can also quickly make a nice rolled hem. Like a serger, a cover stitch machine has a looper, but it doesn't have a blade. Cover stitch machines are used to make knit hems and chain stitching. And most sergers that can handle more than 4 threads can do both a cover stitch and a serge stitch. Coverstitch machines can use as few as one thread or as many as four or five. Most of the time, there will be two top threads and one looper thread. For the straight stitch part, the top threads go through needles. The bottom side of the stitch has the looper thread, which gives the stitch its stretch.