Controls are the things in your toolbox that have a specific functionality. Textboxes, Buttons, ProgressBars... these are examples.
Each control is defined in a class that contains all the code for doing the special things it does: for instance, the code to return the information in the textbox.
VB.NET allows you to overwrite those functions if you want it to do something slightly different. I created a new type of control with a listbox and a button... it toggles "Select All" and "Unselect All" whenever you click the button. Putting this in a control allows you to package it and use it elsewhere... so once I created the control, all I have to do is reference my .dll file and declare a new SelectAllListBox object. Saves time because I can just plug in my pre-configured package whenever & wherever I need, and I'll have something that works just like all the other ones in my program.
hth
Ben
A programmer was drowning. Lots of people watched but did nothing. They couldn't understand why he yelled "F1!"