The term letter case or just case is used when discussing the difference between lowercase, uppercase, or capitalization.
- this sentence is written in all lowercase
- THIS IS ALL UPPERCASE (also called ALL CAPS)
- Capitalization Is When The First Letter In Words Is Uppercase
There are different ways of using capitalization in writing, depending on the medium and the preferred style of the publisher/author.
Typically in article titles you don’t capitalize words like “a, an, the, to, on” but you capitalize important words.
Capitalizemytitle.com has a good description of the various capitalization styles.