Back when I was a pouty-pre adolescent (no goths yet), I loved sewing. Girls had to take home-ec, which involved learning to sew. I started making very weird clothes, which in the days of dress codes (no pants on girls), made me even less acceptable.
Beneath the needle (as the GIF shows at a very slowed down speed) a hook rotates, capturing the thread from above and looping it around another thread, this one reeling from the bobbin below. The two threads interlock around the layers of fabric, binding them to one another.