The is the most common stitch made by most sewing machines. Its created by a top thread locking into a bottom thread.
Chain Stitch.
A chain stitch is created by looping the bottom thread around the top thread. It is less secure than the lock stitch because if one end comes undone the whole stitch will unravel.
Double Chain Stitch.
Same as a chain stitch but made with two needles.
Eyelet/Keyhole.
This machine sews the holes for buttons. I have not seen a diagram for this actual stitch but I have a very interesting video of a machine in action.
Keyholer in action.
Bar Tacking.
This stitch is mainly used to attach belt loops and back pockets. The tight zigzag patern of this stitch allows it to hold a great amount weight, up to 400 lbs!