What is the key difference between extractive and abstractive text summarization?

The key difference between extractive and abstractive text summarization lies in how the summary is created. Extractive summarization creates a summary by selecting and concatenating sentences or phrases directly from the original text. It identifies the most important sentences based on various criteria such as term frequency, sentence position, or similarity to the overall topic, and then combines these sentences to form the summary. Abstractive summarization, on the other hand, generates a summary by paraphrasing and rewriting the original text. It understands the meaning of the text and then creates new sentences that convey the same information in a more concise way. For example, an extractive summary of a news article might consist of the first few sentences of the article, or the sentences that contain the most frequent keywords. An abstractive summary, however, would rephrase the main points of the article in a new set of sentences, potentially using different words and sentence structures. Extractive summarization is generally simpler to implement, as it does not require generating new text, but it may result in summaries that are less coherent or less informative than abstractive summaries. Abstractive summarization is more challenging but can produce more fluent and informative summaries.