Definition from Merriam-Webster: "a restatement of a text, passage, or work giving the meaning in another form" [1].
In other words: e.g. I take a sentence from a text and rewrite it using different words/synonyms without changing the meaning of the original sentence. It's important to mention that even if we paraphrase, we need to cite the source.
In academic texts it's necessary to use paraphrase because it shows, that we understand the source well enough to write it in our own words. It also helps us not to use direct quotes that often, which should be used infrequently. [2]
Paraphrase can be also used to shorten a longer text to make it easier for the reader to understand.
Example:
Original: I went to the man to talk to him about it.
Paraphrase: I approached the man to discuss it with him. (citation of the original source)
Sources:
[1]: https://www.merriam-webster.com/dictionary/paraphrase
[2]: https://www.latrobe.edu.au/students/admin/academic-integrity/referencing-help/paraphrasing
Zdeněk Staněk 527040