Summarising or summarisation are synonym terms and describe the activity (or “the process”) of developing the summary of a text, article, book, or video sequence.
Summarising is more than retelling: it involves distinguishing important from unimportant information and restating it in as few words as possible.
Summarisation promotes a deep understanding of information: you should identify relationships among main concepts in a text, and link them to your prior knowledge.
Summarisation is considered by specialists to be among the Top Ten most effective learning strategies in the history of education.