Scanners

What they do
They allow you to digitally copy images and/or text. Scanned material can be rendered into graphic or text files and formats.
 
Quality to consider before purchasing one
There are several types of scanners suitable for the home office environment:
1) Flatbed Scanners, the most popular scanning technology available, are designed with the scanner horizontally mounted (like a bed!) to scan in pictures, documents, book and magazine pages, and other material.
2) Photo Scanners move a photo over a still or stationary light source.
3) Transparency Scanners are especially useful for slides as they pass a light through an image to scan.
4) Handheld Scanners are usually about the size of a hand. These scanners are the most inexpensive scanning device, and can be especially useful where space is limited.

The parameters to consider are the quality of the sensor, the resolution, the reliability over time and possible additional accessories such as the slide reader.

My suggestion is to choose a flatbed scanner (A4), avoiding smaller scanners which up until a few years ago were very popular.

A maximum resolution of 1670 or 2400 should be sufficient for scanners for personal use. Pay attention to the actual resolution indicated on the scanner rather than the interpolated resolution which is generally greater and of no use to you (it is similar to a resized image, which you can do yourself with the appropriate software).
The cost of a good quality flatbed scanner (A4) for personal use is between 70 and 200 USD.
Brands to keep in mind (Scanner sale)

1) Epson
2) HP
3) Canon