Adventure Games and RPGs (gaming wise) goes hand in hand, regardless they both follow a very simple thing. They stick you in a role, and you play as that role. Really RPGs are just Adventure games with random battles/any turn based fighting.
i wrote my college thesis on rpg's brah. there are three things common in
all role playing games
1. you control, to some degree, the growth of your character
2. rely indirectly on the character's skill to succeed in challenges, not the player's skill
3. percentages or rolls are used to simulate random chance
zelda, for example, isn't an rpg because you're in control of link's actions. your success at beating the game is determined by your skill as a player. diablo is an rpg because even though you directly control the character, their success is primarily determined by their personal skills.