It's a lot to take in if you like theorycrafting, but don't sweat these differences too much.
Each race in World of Warcraft comes with special bonuses towards certain crafting professions and a unique skill only they can use, but that skill varies between Classic and retail. For example, in modern WoW, humans can break out of stun effects while blood elves can strip a positive buff off nearby mobs or players. It's a lot to take in if you like theorycrafting, but don't sweat these differences too much. Above all else, pick a race of which you enjoy the fantasy and aesthetic—that'll be the one you're most likely to stick with.