These words describe something that is attractive, nice to look at.
The word beautiful is stronger and more complete. You could describe a
spectacular sunset as beautiful, or a very attractive woman in a fancy dress as
beautiful.
The word pretty is more informal and superficial. A nice arrangement of flowers
could be described as pretty. You can also describe girls, women, and clothing as
pretty – but it is not as strong as beautiful.
The word cute is also informal, and means something is attractive in an adorable
way. It is often used for children and animals. When describing an adult (man or
woman) as cute, it means the person is attractive, but not SUPER attractive (for
super attractive we would say the person is beautiful/gorgeous – for a woman –
handsome – for a man – or hot, has a sexy connotation, for both women and men).
For boys and men, we don’t use pretty or beautiful – we can use handsome (usually
for men), hot (also for men) or cute (usually for boys).