If all the technical terms seem completely baffling, the glossary below should help you to make better sense of them:
Feed dogs: are saw shaped teeth that move the fabric through the machine. As the needle stitches, the feed dogs grab the fabric, moving it under the presser foot. The term “drop feed dog” means that the feed dogs can be used in either the up or down position. When the feed dogs are down or “dropped”, you can use the machine for work such as machine embroidery where the fabric can be moved freely under the needle.
Presser foot: The presser foot holds the fabric in place against the feed dogs so that it doesn’t move about while you are sewing. You can buy specialised presser feet for different jobs.
Needle plate: The needle plate is the part of the machine which fits over the feed dogs on the bed of the machine, with a hole that the needle passes through.
Knee lifter: A knee lifter is a lever which can be pressed with your knee, allowing you to lift the presser foot and drop the feed dogs
without taking your hands off the work. This is useful for quilting, sewing around curves and appliqué.
Free arm: A free arm is a cylinder on the bed of the machine which allows you to sew items such as sleeves and trouser legs. This usually works by detaching a piece on the base of the machine, leaving the arm protruding.
Bobbin: A bobbin is a small spool for holding thread. Sewing machines use two threads to make a stitch: The needle thread, coming downwards from the top of the machine and the bobbin thread coming upwards from under the needle plate. Thread is wound onto the bobbin before you begin sewing, then fitted into a bobbin case and put into place.
Stitch selector: On more basic machines, the stitch selector is usually a dial which allows you to select different stitch types. On computerised machines this is done by pressing a key or using a touch pad.