An online keyboard is a software that allows users to type characters. Normally an online keyboard provides on screen keyboards with clickable buttons to type characters. In this case, the typing is done using a mouse or a finger on touch screens.
An online keyboard can also use a physical keyboard to type characters. For example, you can use an English keyboard to type German characters and the virtual keyboard software automatically converts the English letters to that of German.
Why use an Online Keyboard?
The computer or device you are using does not support your language.
You are using a computer in a café in a foreign country.
You are multilingual and you do not want or know how to change your computer settings.
The characters you want to type are missing from your physical keyboard.
You want to bypass a key logger on a compromised computer.