These are the different levels culling algorithms can work on.

Triangle Level

Description: Determine for each triangle if it should be culled or not.
Primary goal: Minimize triangle count.
Culling technique example: BSP 
Usage: Not used anymore, cost to much CPU.

Object Level

Description: Check each object (a group of triangles in one buffer) if they should be culled or not.
Primary goal: Minimize triangle count and keep state changes low.
Culling technique example: View Frustum Culling of Bounding Box Hierarchies
Usage: Often used.

Batch Level

Description: Will check whole batches (a group of objects in one buffer)  if they should be culled or not.
Primary goal: Minimize draw calls and triangle count.
Culling technique example:  Uniform Grid Culling
Usage: Often used.