Touch Screens work  instantly  with  All  programs - Just like a mouse.
    Simply touch the screen to respond, explore or create with your computer.
    Choose menu items, press buttons, move objects - simply by touching the screen.

ADD-On 
 touch screens are external frames with a clear see-through touch screen.
    They mount outside onto the monitor bezel. The controller is built into their frame.
    Some require power from a wall connection, others tap into the keyboard power.

BUILT-In 
touch screens are internal, heavy-duty touch screens mounted directly onto the monitor. Controllers are usually inside the monitor but can be external. 

Type:

Resistive

Infrared Capacitive
Activation: Pressure Sensitive Light grid interruption
Electrical charge
Antiglare: Minimal Zero Yes
Clarity: Medium Best medium
Damaged by Very sharp objects Water
Very sharp objects
Can handle dirt
Good Good Good
Made with Hardened acrylic plastic IR LED Components.
Glass
Durability (MTBF) Good Very Good Good
Warranty 1 Year 1 Year, optional 2 year 1 Year
Works with Finger, glove, stylus Finger, glove,soft stylus Finger
Other Best Price, precise fit Best Clarity, easiest install Most accurate, no bezel

Add-On touch screens are Infrared type.
Built-In touch screens can be Resistive or Capacitive(pcap).

Touch Screen Features:

  • Convenience of push button control
  • Easy enough for a child to use
  • No dragging mouse to each starting point
  • More intuitive than other input devices 
  • Low maintenance.
  • No training needed (push button control)