Can you explain the difference between a soulbond and a headmate? I’m really not understanding and I need to because of my situation.

The short answer is a soulbond is a type, or subset of, headmate.

A headmate is any fully realized independent person/entity that shares mental space and a body with one or more other persons/entities. Essentially, two or more people sharing one body.

A soulbond is a specific type of headmate. Soulbonds are fictional characters that share mental space with a person, who is called a soulbonder. Soulbonds may be different from other types of headmates in that soulbonds generally fill an advice-giving or protective role, or have otherwise positive feelings toward a specific other person in the body, the soulbonder. 

Soulbonds often seem to be drawn towards high levels of emotion toward them, and can be deliberately sought out.

Soulbonding is often thought of as something very personal and meaningful, and bonders have deep relationships with their bonds. Some people have bonds that are more parental, and some more friendly, and some even romantic.

Soulbonders can have many soulbonds, or just a few, or even just one. Sometimes soulbonds come and go, frequently or over long periods of time.

Hope this helps!