Annotation is a note made while reading text to deepen understanding, such as underlining main points, circling confusing words, or writing questions. It has been practiced since texts first existed and helps readers slow down to analyze meaning, such as a student's notes on connotations in Charlotte's Web. Effective annotation for grades 6-8 includes underlining, circling, using question marks and exclamation points to note reactions, and drawing arrows to indicate connections within or beyond the text.