can u help me y do some animals have babys an some have eggs...../?

Answer 1

Yes, that is correct.

Examples -
Eggs = birds, including chickens (check your fridge, they usually come in boxes of 6), most reptiles
Babies = humans (you :-) ) and you might see eg. you pet cat give birth, most mammals

Answer 2

Having eggs is the older practice - the earliest animals all laid eggs in the ocean, and as animals gradually colonized the land, they still went back to the water to lay eggs (eg amphibians). Reptiles developed means to survive totally on land, including eggs with hard shells to restrict water loss, and that's the state for reptiles, birds and a few mammals today. Some reptiles and fish retain the eggs inside the body until they hatch, so the young are born live, but placental and marsupial mammals go one better - they don't make an egg at all, which allows the young to develop unrestricted by a shell, and also saves a certain amount of energy expense. Of course, every choice comes with costs and benefits.