What is the difference between a toolstrip drop-down button and a toolstrip split button? What is the use of toolstrip container?

Answer:

The difference between these two is that a toolstrip split button is a combination of two controls that is a push button and a drop-down button where a toolstrip drop-down is a single control.

Basically this is used to contain controls such as ToolStrip, MenuStrip, and statusStrip, so that these controls can be docked and moved at the run time.