SEM, or Search Engine Marketing, used to be commonly referred to as an umbrella term including both paid search and organic SEO (Search Engine Optimization).
Nowadays, Search Marketing is the umbrella term, while SEM increasingly refers to paid ads on search engines like Google, Bing, Yahoo or Yandex.
Whichever acronym you prefer to use (SEM, SEA or PPC), paid search is here to stay and there are several reasons why you should be using this tool in your digital marketing toolbox.