I understand what/how to do VBO's but I don't know how to link it with game dev. If I have a HUD, entities, effects, terrain, do I have one VBO to handle all th

I understand what/how to do VBO's but I don't know how to link it with game dev. If I have a HUD, entities, effects, terrain, do I have one VBO to handle all that data (and update it in my game loop)? Or should I split the VBO's into HUD/entities/effects/terrain/etc?