Yes, in some form. Many people are surprised to learn SEO isn't a single process that takes place. Google has thousands of different factors it weighs in order to rank your website. How fast your site loads, ease of use on mobile, how long people stay on your site, and more are all taken into consideration.
On-page search engine optimization is almost always a good idea. This ensures your website is coded to correct standards and the content on your website is structured properly. This makes Google happy and gives you a boost within their rankings.
Off-page search engine optimization is more complex and primarily involves something called "backlinks". These are links on other websites pointing to your website. Getting authentic quality backlinks is very time consuming and difficult. Some agencies will try to "game" the system by creating fake backlinks. Google is getting very good at figuring out if a backlink is fake. If you're caught, you can be completely delisted from Google searches. Remember, if it sounds too good to be true, it most likely is.