Difference between the fruits
Precisely, in many cultures the main difference between a banana and a plantain is that you have to cook a banana plantain before you can eat it, while you can eat a fresh ripe banana anytime without having to cook it. In some West African grocery markets, plantains are typically bigger than bananas. Ripe bananas usually taste sweeter than ripe plantains.
Difference between the trees
It can be really challenging to describe just in words the difference between banana trees and plantain trees, but it is possible. There is no visible distinction between the two, unless each tree has fruits in ripening stage.