Each word of a person's name begins with a capital letter. An initial stands for a person's name. It is a capital letter with a period (.) after it.
Joanne Kathleen Rowling wrote the Harry Potter series.
J.K. Rowling wrote the Harry Potter series.
Thomas Alva Edison invented the lightbulb.
Thomas A. Edison invented the lightbulb.
Rosa Louise McCauley Parks was a brave woman.
Rosa L.M. Parks was a brave woman.