Lynda.com (available thru the Library) has a lot of information on this.
3. Three technical terms:
lossy/lossless comprehension--- In lossy comprehesion we might make the image file more compact, have it look great as a thumbnail, but when we enlarge the image back up lose some of the detail. In lossless comprehension we don't lose the detail.
dithering - this is a method of using fewer colors but scattering them a little around a point to make it appear as tho' we have more colors.
jaggies - these are the jagged lines you get when you try to enlarge a curve, such as a circle, and don't have a fine enough grid to make it look like a curve. You've all seen these.
4. What to read:
a. https://sanstudio.com/tech/GraphicFileTypes.html Read about Web-Graphics file formats. (Don't bother with Postscript files types etc.)
b. https://www.webstyleguide.com/wsg3/11-graphics/5-web-graphics-formats.html is a short summary
c. OPTIONAL - if you want more examples look at https://1stwebdesigner.com/image-file-types/