Answer:
A basic sewing machine will sew a straight stitch, attaching two pieces of fabric to one another. Almost all new machines will have length/width control and will also do zig-zag stitching. As you go up in price, however machines will come with many more features, such as automatic threading, decorative stitches, stitches that bind the edges of fabric, embroidery, stitch size control, and many more features.
Sewing machines operate using two threads, a top thread and a bobbin thread. The sewing machine wraps the threads around each other, creating a much stronger stitch than in hand sewing.
There are also sergers which use 3-6 threads that are used for binding the edges of fabric. They are mostly used in commercial clothing manufacturing