A variant is another version of something. You could say chimps and apes and gorillas are variants in the primate family.
Words often have variants, spellings that vary from region to region or country to country. The British colour and the American color are variants. When a movie or TV show is remade or casts a new actor — like with the string of James Bonds — you could call those movies variants. Where there are variants, there is variety — things aren't all the same.