What is letter spacing? Letter spacing is adding extra space between letters. It is the result of positive tracking, with tracking referring to the average space between letters.
Why would someone letter space anything? Well, something in all caps or small caps might look better when letter spaced. For example:
HELLO looks better than HELLO.
So why don’t you do it to lower case letters? Well, lower case letters like to get cozy with each other. They’re meant to sit pretty close together so their shapes can flow together. For example:
hello looks better than hello.