Do what George Martin does: DROP, WAIT, then ELABORATE. Basically, you drop the information and act like your readers already know about it, however in the next scene or chapters, the information shows itself naturally usually through the setting.
Example:
Protagonist states that he must avoid hollows when crossing the forest in the first scene, but he doesn't elaborate on it since story-wise it doesn't make sense for him to say it. However, in the next scene the protagonist, while carefully walking through the forest, stumbles upon a floating semi-transparent figure with a ghastly face. The figure spotted him and let out a screech and chased him, then the protagonist cursed and runs away from it.
This is what George Martin usually does in his song of ice and fire books. He drops an information then reveal what it means/show in the next scene or chapter. In my example, we, the readers, don't know what hollows is aside from the fact that it's present in the forest and deadly enough for the protagonist to steer away from. So when we spot the semi-transparent figure chasing the protagonist and the protagonist reacting in such a way (cursing and running), we usually automatically link the figure with the term hollows.