Once you've used it, it's hard to go back to dial-up.
Some modems sit outside the computer and plug into the serial port or USB port.
USB is more convenient and reliable, but make sure your computer has a USB port before you buy. Some modems are cards that fit into slots inside the computer. These internal modems are cheaper, but don't buy one unless you are comfortable with the idea of opening your computer. Avoid modems called software modems or Winmodems. They're generally cheaper, but they can slow your computer.