Well, if you look in your TSL Reference Guide, you'll get more information on it.
But basically, they allow interaction with the user.
Create_input_dialog(Message); is for just a popup to the user, and you put whatever you want to tell them at a certain time
Creat_list_dialog(title,message,item_list); allows you to give the user choices inwhich to pick (items in the list are seperated by commas within the quotes i believe) This is useful when having a "main" script calling others depeding on what you want to do
Create custom dialog is exactly what it says, you get to create a custom dialog. and same with the last one
I dont know much about the last two, so I cant help you there.
We used create_custom_dialog() in a script for configuring a development environment for WinRunner.
We placed an "Execute TSL"-toolbar button into WR that calls this script.
In this script a custom dialog comes up in which you can select for which environment you want to develop tests. Then the script loads libraries, opens GUI Maps, ... - depending on the selections you made in the custom dialog.