There are two kinds of fixative: there is workable fixative which allows you to go back in and work on the drawing even after spraying it. There is permanent fixative, which you cannot work back into.
Charcoal drawings are very fragile, and thus are susceptible to damage. Even a slight smudge of a finger can ruin a carefully drawn area. One option is to use fixative, a material you can spray over the surface of a charcoal drawing to make the charcoal adhere more permanently to the paper. Always spray fixative on your drawings outdoors, the fixatives have chemicals that are dangerous to breathe. Some people use hairspray instead of fixative, which I do not recommend. If you are at all concerned about your drawing lasting long term, hairspray is a bad choice because it is not an archival material.
I personally have never been a fan of fixatives; while they do make charcoal drawings more resistant to damage, you will notice that your charcoal drawings will darken slightly after spraying it with fixative. The darkening is not that dramatic, but it’s enough that I definitely notice the difference in my drawings. A compromise is to gently place a sheet of newsprint of tracing paper over your charcoal drawing when you store it, and know that you might have to do some last minute touch ups before displaying the work.
Art Supply Tips
Charcoal drawing supply set
erasers for charcoal drawing
white plastic erasers
layering & mixing charcoal