Do you have to use a hoop when doing cross-stitch?

I’m going to stay with a friend for 3 weeks over the holiday season, and I’ve decided doing some cross-stitch would be the ideal project-I-wouldn’t-ordinarily-have-time-to-do to fill my time while they’re at work. Also, it’s an ideal thing to be able to pack as easily as clothes etc.

I’m just trying to work out if I need a hoop to do cross-stitch, or is a hoop really only needed for embroidery? Would a hoop be a good idea? Would I do any damage by using one?

Any other great cross-stitch advice for a committed beginner?