A touchpad is designed to be controlled with your finger. By sliding your fingertip along the surface, you can move the cursor on the screen. Similar to a mouse, touchpads can detect acceleration as well as linear motion. This allows you to have refined control with slow movements and quickly move the cursor across the screen using a fast motion.
Some touchpads have two buttons below them, which correspond to the left-click and right-click mouse buttons respectively. In modern laptops, the buttons may be hidden in the bottom portion of the touchpad. This allows for a larger touchpad surface, but you can press the lower left or lower right section of the touchpad to click the buttons.
Touchpads may also include multi-touch technology, which is common on touchscreen devices. This means you can use multiple fingers to perform different actions on your computer. For example, some programs allow you to use two fingers to pinch and zoom in or out on a document or image. You may also be able to twist two fingers on a touchpad to rotate an image left or right. Some programs allow you to swipe left or right to go back in a web browser or jump to another page in a document.
NOTE: There is no difference between "touchpad" and "trackpad," so the two terms can be used simultaneously. However, "touchpad" is commonly associated with Windows computers while "trackpad" typically describes the touch controls built into Macs and Apple-branded peripheral devices.