A paraphrase restates a short passage and can be as long or longer than the original passage. A summary restates or highlights the writer’s main point(s) and is much briefer than the original material.
Whether you use a paraphrase or a summary, you need to completely understand an idea before attempting to put in into your own words. Otherwise you could misrepresent what the source is saying. OR your paraphrase or summary could end up echoing or resembling too closely the wording and sentence structure of the original material -- which is plagiarism, even if you cite your source.
When paraphrasing/summarizing:
use words that are distinctly different from the original material
put borrowed phrases in quotation marks
use a different sentence structure so that you don’t plagiarize by following the original wording too closely.
clearly mark the boundary between your text and the material you’re paraphrasing or summarizing.
Here are some helpful resources:
Avoid Plagiarism in Research Papers with Paraphrases & Quotations