The bobbin is that small little spool that forms the bottom thread in the stitch.
This information follows on from How To Wind Thread Onto the Bobbin >>
I only have front loading machines with a bobbin case so that is the method I’ll describe here. Some machines have a drop-in or horizontal bobbin. The best tutorial I’ve found for loading those is here. For those more into moving pictures here’s a good link.
Step 1: Pull out a 10cm tail of thread from the bobbin.
Step 2: Remove the bobbin case from your machine by lifting the little lever near the central pin.
Step 6: Go fishing – Hold the top spool thread with your left hand, turn your balance wheel towards you so that the needle does a full revolution (goes down into the machine and back up again). The top thread will pick up the bottom thread on its way through.
Step 7: Gently tug on the top thread so the loop of the bottom thread pulls out from between the feed dogs.
Step 8: Use a pin or similar to swish the end of the bottom thread out.
Step 9: Close your bobbin compartment cover.
You’re all done and your machine is now threaded and ready for sewing.