Bringing thread from a front loading bobbin up through the metal face plate in order to sew requires you to stick your fingers under the presser foot and push the thread through. Bobbin-Thread Lift brings the thread to the surface making the process easier. Free Arm
A machine with Free Arm capabilities allows a portion of the flat bed to be removed creating a narrower sewing surface. Manual vs Computerized
Manual machines generally have fewer stitches and all of their components are controlled by hand. Computerized machines have touchpad controls that can recommended stitches, pressure foot tension and low bobbin thread. Stitches can be saved to memory and can often stitch patterns and letters on their own. Needless to say Manual Machines tend to be the less expensive of the two. Needle Down
When sewing a corner, it’s easiest if the needle is still down through the fabric, but in the past it was necessary to time the stitch just right or lower it in to place with the wheel. This feature allows you to automatically choose the position of the needle quickly and easily. Top Loading Bobbin
Traditional sewing machines kept the bobbin in a metal compartment at the front of the sewing machine. They were difficult to load and often had to be untangled. Top Loading Bobbins let you drop the bobbin into place and sew. Some models have clear covers that allow you to keep an eye on how much bobbin thread remains.