What is the fundamental difference between object mode and edit mode?

Question

I'm trying to find out what is the difference from the 3D engine's point of view between these 2 modes. On a model with a lot of vertices, the editing mode tends to lag a little when you rotate the 3D view for example.

Answer 1

Edit mode is made for modify the geometry of your mesh, like adding vertex, faces, and so on. In object mode you use your mesh as an unique entity, and you can edit it's properties (ie: position, rotation and so on). So:

• Have you to work on some aspect of your object? Have you to sculpt it? Edit Mode.
• Have you to place your object on the scene, choose it's size, apply on it some modifier? Object mode.