Ray B says:

I have investigated these and can say this the GIF is a very simple picture of what goes on. There are several different ways to get the upper thread to loop around the lower thread. There are three basic ways it has been done in the past and Singer has used all three from time to time. There is an oscillating hook that catches the upper thread behind the bobbin thread and carries it a little more than halfway around to the front of the bobbinwhere it releases to go back and catch the next needle thread. Once the thread is released the tension becomes critical becuase the thread arm pulls the needle thread w quickly up to tighten the stitch. The bobbin just sits loosely in a cage so the needle thread can pass around it.
The Pfaff and the Viking and the singer 201, 301 and most industrial sewing machines use a full rotary hook that revolves twice for each needle stroke. Once to catch the thread, fully rotate and then release it and once without any thread to get back to position to catch the thread again.
The orientation of the hook and the bobbin varies with machine design. many are perpendicular to material motion (vertical or horizontal) but some are oriented exactly the way the gif shows (only running twice as fast on the bottom as the top). The critical parts of the design are the hook timing, the thread arm pull rate, the upper and lower friction on the thread (tension at critical junctures) and the cross sectional and hole shape of the needle and its orientation to the hook.
A lot of the industrial machines can stitch 5500 stitches per minute. At those speeds even the type and twist of the thread becomes critical.
Now if someone would only explain to me how a serger works with no bobbin and four spools.