Lwjgl OpenGL Help

Question:
Question;
I've made my top-down minecraftlike game to a point. Dynamic/adjustable types, basic entities, player movement, a worldgen...
However.
This whole time I didn't understand that I needed to code the game to use a Video card via OpenGL and stuff, so the game lags like a whore by only using CPU power to display everything.
So, I'm looking into lwjgl(Yes, I'm using Java), and following some tutorials I understand 'kinda' how to draw basic 2D shapes using OpenGL.
However, I am stuck.
There seem to be multiple ways of displaying a graphic?
DisplayLists, and Vertex Buffers?
I have NO idea what I am doing here.
Do I somehow have the video card calculate the layers of images I am making?
Or is it 'purely' for display?
Sorry if the answer seems obvious, but although I know coding enough to do alot of stuff, this OpenGL stuff seems way over my head and I'm not exactly sure what computer logic I am trying to follow.

>>1
There are a lot of things that serve the same purpose but carry different levels of restrictions. Restrictions help faster implementation of the feature, so you should use the most restrictive method that still enables you to get what you need. Just take your time, start with something simple. Then work your way up to the point where you feel comfortable with implementing a game in it. Although it sounds like you are just doing 2D graphics?