Google decides which pages on your site are important or most relevant. You can help Google by linking to your important pages and ensuring at least one page is well optimised amongst the rest of your pages for your desired key phrase. Always remember Google does not want to rank ‘thin’ pages in results – any page you want to rank – should have all the things Google is looking for. That’s a lot these days!
An SEO meta description is a brief description of content found on a web page. The meta description is shown to users in search engine results pages to help them decide which search result to click on. Meta descriptions are not a ranking factor in the eyes of a search engine, but they can influence how many people click on a result -- which directly affects the result's organic ranking.
QUOTE: “So if you have different parts of your website and they’re on different subdomains that’s that’s perfectly fine that’s totally up to you and the way people link across these different subdomains is really up to you I guess one of the tricky aspects there is that we try to figure out what belongs to a website and to treat that more as a single website and sometimes things on separate subdomains are like a single website and sometimes they’re more like separate websites for example on on blogger all of the subdomains are essentially completely separate websites they’re not related to each other on the other hand other websites might have different subdomains and they just use them for different parts of the same thing so maybe for different country versions maybe for different language versions all of that is completely normal.” John Mueller 2017
Robots.txt is not an appropriate or effective way of blocking sensitive or confidential material. It only instructs well-behaved crawlers that the pages are not for them, but it does not prevent your server from delivering those pages to a browser that requests them. One reason is that search engines could still reference the URLs you block (showing just the URL, no title or snippet) if there happen to be links to those URLs somewhere on the Internet (like referrer logs). Also, non-compliant or rogue search engines that don't acknowledge the Robots Exclusion Standard could disobey the instructions of your robots.txt. Finally, a curious user could examine the directories or subdirectories in your robots.txt file and guess the URL of the content that you don't want seen.
SMM refers to both organic and paid digital marketing efforts on social media networks like Facebook, Twitter, and LinkedIn. Social media marketing encompasses many different activities and many consider this to be the future of digital marketing. While social media channels become the hub of activity online in the modern age, this is where consumers engage each other in conversation. Furthermore, it’s also the nerve center of business and brand engagement for large subsets of the population.
QUOTE: “They follow the forms you gather data you do so and so and so forth but they don’t get any laws they don’t haven’t found out anything they haven’t got anywhere yet maybe someday they will but it’s not very well developed but what happens is an even more mundane level we get experts on everything that sound like this sort of scientific expert they they’re not scientist is a typewriter and they make up something.”  Richard Feynman, Physicist 1981
The SEO starter guide describes much of what your SEO will do for you. Although you don't need to know this guide well yourself if you're hiring a professional to do the work for you, it is useful to be familiar with these techniques, so that you can be aware if an SEO wants to use a technique that is not recommended or, worse, strongly discouraged.