Like clothing and shoes, keyboards have different sizes too, they are Full-size, Tenkeyless, and Compact. For keyboards, size matters because they are designed for different purposes. Knowing the keywords and differences can help you get to the right keyboard much faster next time you see thousands of ambiguous Amazon keyboard titles.
This is the most standard keyboard with everything a keyboard should include: the standard key section, the function section with arrow keys, and the numeric pad section. Full-size keyboards usually have a few extra programmable function keys that can benefit professional users to customize shortcuts in software. If your work contains many repetitive paths and needs to use a keyboard to its fullest efficiency then you will want the Full-size.
Ten key is another name for the numeric pad, so obviously, the tenkeyless keyboard is a full-size keyboard minus the numeric pad section. Some left-handed people with data entry jobs prefer to have the numeric pad by their left-hand side so they usually use a tenkeyless keyboard and a numeric pad separately.
There is no single unified keyboard layout for the compact size, but it is safe to say a compact keyboard should include as much feature as possible in one keyboard section. Compact keyboards are like native laptop keyboards, but usually better. They are best for travelers because of the relatively small size and the lighter weight. I personally prefer this size best because it feels natural for a frequent laptop user like me.
And one more thing... Mini/Foldable Keyboards
Designers push the limit really hard so there's even mini/foldable keyboards. These keyboards are the size of a smartphone, you can put in your pocket easily. These are not the most comfortable keyboards in the world, but hey, they get the job done so they are still better than soft keyboards (the one on your touch screen).