There are several ways that SEO firms improve your website’s rank in the search engine results pages (SERPs).
First, they’ll conduct a site audit to find things that are preventing your site from ranking well. Then, they’ll fix those problems, usually with on-site SEO.
Next, SEO companies use a tool like SEMRush to research keywords relevant to your brand. Then, they’ll optimize your site for those keywords.
Finally, they’ll build a backlink profile so other sites are passing PageRank to your own website, and build a strategy using content marketing, social media, PPC, and other factors to continuously boost your rank.