Learn what a selector is at W3Schools.
A combination of habit and the use of hyphens has led me to really enjoying the use of lowercase naming.
Using a hyphen provided for a solid foundation for my website design skills because it's just easier to read. Before that I was switching between upper and lower case names constantly.
From left to right grouped function description
Naming classes and IDs this way may seem awkward when reading a name, but I'm betting it's the organized way to go.
- h1, h2, h3, h4, h5, h6