What is the meaning of annotating?

noun

• The act of adding notes.
  • synonyms: annotation

verb

• Add explanatory notes to or supply with critical comments.
  • usage: "The scholar annotated the early edition of a famous novel"
  • synonyms: annotate, footnote
• Provide interlinear explanations for words or phrases.
  • usage: "He annotated on what his teacher had written"
  • synonyms: gloss, comment, annotate