In a famous example, Colorless green ideas sleep furiously, you are okay from the point of syntax. The words are in the right order, adjectives describe nouns, adverbs describe how verb were done, etc.
However, it has no meaning. Semantically, it's meaningless.
On the other hand, "you me show pictures?" is a mess syntactically, but I know you want me to show you the pictures I'm holding - its meaning is clear.