A scanner is a piece of hardware that you can buy for your computer that allows you to 'scan' or transfer photos, hand drawn pictures or other objects into your computer.
Most scanners come with software included so you can immediately scan items. They also come with an instruction sheet or manual to teach you how to use a scanner. If yours does be sure to read these instructions.
If you are unsure about how to scan, Graphics Software Guide Sue Chastain can teach you How to Calculate Image Dimensions before scanning, How to Save your scans, as well as, teaching you about dpi, ppi and resolutions, important terms to understand when scanning.
If you don't own a scanner many office supply stores, libraries, computer stores and schools allow you to use. Some for a small fee.