Most laptops, tablets and smart phones built in the last few years will have a webcam included. A tech-savvy friend or relative may be able to help you figure out if you already have a built-in webcam in your computer.
If you have a laptop (this will not work on tablets or smart phones) you can also follow the instructions on this website to see if you have a webcam: http://mailvu.com/testCamera/TestYourWebCam.html