It has come to my attention that the word bobbin in the world of fiber can be confusing. There are a lot of particular products that are called "bobbins". If you're new to the world of fiber, that can be a bit of a stumbling block.
This post contains photos of the fiber things that are most likely being referred to. You'll be able to make an educated guess if you know whether the speaker is discussing a tapestry, fabric weaving, sewing, or spinning project. All of them are things that hold yarn in some form or another.
