A meta description is a blurb of text that provides a brief description of a webpage. This text appears as a meta tag in a page’s HTML code. … Text from SEO meta descriptions also appears on search engine results pages (SERPs).
This is the kind of SEO that you're probably familiar with. On-page optimization includes all of the things that your readers will see.
Defining off-page SEO is a bit more difficult. The first and arguably most important part of off-page optimization is link-building.
Some people classify technical SEO as a subset of on-page SEO, but we'll be treating it as a unique type here.
While many businesses only operate online, there are still thousands of companies that have a physical location where they need customers.
Much like app store optimization, YouTube SEO is a niche type of optimization, but it can make a big difference in how much traffic you're getting.
Google and Bing aren't the only search engines out there. App stores—especially Apple's App Store and Google's Play Store—get a phenomenal amount of searches every day.