The Splitter control enables you to resize controls that are docked to the edges of the Splitter control at run time. When the user passes the mouse pointer over the Splitter control, the cursor changes to indicate that the controls docked to the Splitter control can be resized. The Splitter control enables the user to resize the docked control that is immediately before it in the docking order. Therefore, to enable the user to resize a docked control, dock the control you want the user to be able to resize to an edge of a container, and then dock a splitter to the same side of that container.

That is if you want to split the layout of your Windows Forms window into two parts either  a left and right half or a top and bottom half. By using the Splitter control, you can present a resizable view to your user.

To add a Splitter Control in your window form, you will drag Splitter control from toolbox into your window form just like other control such as textbox, button controls etc.  The Splitter control will have two sub containers in it. They can be accessed through the Panel1 and Panel2 properties.