To write an Argumentative Essay you must research your chosen topic in order to collect information and gain perspective on it. In this you must evaluate the evidence on either side of the topic and develop a concise argument.
An Argumentative Essay gives the writer the ability to demonstrate their understanding of a topic and to present their own opinion on it.
A summary is a brief statement or account of the main points of something. In other words, the writer gives only the main points of something that they have read or heard (Oxford Dictionary, below).
Being able to summarize an article or class project is a great way to demonstrate your understanding of the material. Your professor may require you to summarize your reading for an assignment. And you will certainly have to summarize sources when you write a research paper.