It's pretty simple!
Digital marketing strategies have 2 primary goals:
- Brand the company
- Get Call-to-action (Sales, Call, Feedback, etc...)
And to achieve these 2 types of goals we use 4 concepts to digital marketing:
- SEO (Search Engine Optimisation) - Used for branding
- SEM (Search Engine Marketing) - Used to get Call-to-action
- SMO (Social Media Optimisation) - Used for branding
- SMM (Social Media Marketing) - Used for both
Now, the SEO and SEM are related to Search Engine which is dominantly Google. Yea no doubt even Bing and Yahoo are part of it.
It is simply to work on the website to increase its position in search results for the keyword. You can write blogs, article and what not to share the link to your website, which will popularise it.
Similarly, SMO is to post an article, photo, video of your product or service using appropriate hashtags to get more reach.
SEM is to pay Serch Engines like Google to rank up your website in the search results for the list of keywords instantly.
Google AdWords is the tool used to run various types of ads on Google and its network websites.
Network websites are the websites who display Google ads on their website via Google AdSense.
SMM is to pay Social Media websites like Facebook, Twitter, and LinkedIn to promote your post. You can make payment on basis of clicks or views.
Other channels like PPC and Affiliate marketing, are other forms to promote your website.
This is to ask online celebrities like famous YouTubers or Bloggers to create and share the content about your product or service. This also includes the Social Media accounts will most followers, and the websites with many visitors.
For more check out the answer on How do I hire affiliates?
PPC is Pay-Per-Click, this is to pay for the click you get through the channel. Affiliate marketing, SEM, SMM can be done on the basis of Pay-Per-Click also, which simply means that you will pay only when a person visits your website.
Hope I was helpful!