Sometimes the terms that get used medically, hallux valgus (or hallux abducto valgus) and bunions are used to describe the same thing when they aren’t.
A bunion is the enlargement that occurs on the big toe (hallux) joint, or technically the first metatarsophalangeal joint. Hallux valgus is when the big toe angles in a valgus direction, which is towards the outside. There is debate about if this is valgus or abductus (hence the term hallux abducto valgus and which one occurs in which direction, but that can wait for another day).
Basically, a bunion is the lump and the hallux valgus is the deformity.
So, yes they are not the same thing, but a bunion almost always occurs with a hallux valgus and they are both parts of the same problem.