When you're talking about superlative, you refers to a very specific group, for example: in the yard there are 5 flowers, a blue, a pink, a yellow and etc., but you wanna say that the pink is THE MOST BEAUTIFUL from that group of flowers, or you wanna say that THE blue flower is PRETTIEST than the others.
in a long sentence you use: THE MOST + adjective = THE MOST BEAUTIFUL
in a short sentence you use: adjective + EST = PRETTIEST
espero ter ajudado <3
