Alguien puede explicarme una cosita?

Hola Nia! las palabras "lleno" y "repleto" son sinonimas, los hablantes nativos de epañol solemos decir "repleto" para referirnos a que algo esta excesivamente lleno... muchas veces es usado como jerga, usar la palabra "lleno" es un poco mas formal... pero las dos significan lo mismo. si deseas saber mas del español no dudes en visitar mi perfil! te encantara!... saludos.

Like the other answers say, repleto and lleno mean about the same thing. However, I can think of cases where they are not interchangeable.

After you finish a meal, if you are full you'd most likely say "Estoy lleno" instead of 'Estoy repleto'

Likewise, a glass full of water would most likely be 'lleno' instead of 'repleto'.

'lleno' gives the impression of being 'full', while 'repleto' gives the impression of being 'full to the brim'. For example, 'un bus lleno de gente' might simply mean that all the seats of the bus are taken, or might mean that there is no standing room, while 'un bus repleto de gente' most likely means only the latter, i.e., it is so full of people that there is hardly any standing room left, if any.  So, in a sense, 'lleno' means that something is fairly close to its full capacity, while 'repleto' means that it is at or beyond its full capacity.

Also, you are most likely to use 'repleto' when talking about countable things. For example, a bag of M&Ms would be 'llena' when you buy if from the store. You can open it and force more M&Ms in it; at the time when you can no longer fit any M&Ms in it, you will have a bag 'repleta' of M&Ms.

REPLETO ES ADJETIVO 

LLENO ES ADJETIVO Y VERBO DE LLENAR