What does includes in SEM?

I am little bit confused with above example's, SEM stands for Search Engine Marketing, n according to me SEM is consist of SEO, SMO, Paid search marketing, and digital marketing consist of SEO, SMO, Paid Search marketing, apps ads marketing. Please revert with your point of view if i am wrong.
 
SEM is a type of Internet marketing associated with the researching, submitting and positioning of a website within search engines to achieve maximum visibility and increase your share of paid and/or organic traffic referrals from search engines. SEM involves things such as search engine optimization (SEO), keyword research, competitive analysis, paid listings and other search engine services that will increase search traffic to your site.
 
Short for “search engine marketing,” SEM is usually used to describe the immediate, money-backed portion of search engine marketing that commonly takes the shape of PPC (pay-per-click)/CPC (cost-per-click) search engine results page ads in one form or another.
 
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