If there is a single concept that is the driver of much of the Internet's growth over the past decade – not to mention nearly all of Google's annual revenue of $25 billion – it is the concept of keywords. Keywords are what we type in when we are searching for products, services, and answers on the search engines, an act that Americans performed 15.5 billion times in April 2010 according to ComScore, the web research firm.
Keywords are important because they are the linchpin between what people are searching for and the content you are providing to fill that need. Your goal in ranking on search engines is to drive organic traffic to your site from the search engine result pages (SERPs), and the keywords you choose to target (meaning, among other things, the ones you choose to include in your content) will determine what kind of traffic you get. If you own a golf shop, for example, you might want to rank for "new clubs" — but if you're not careful, you might end up attracting traffic that's interested in finding a new place to dance after dark.
Because someone who is looking for something that specific is probably a much more qualified searcher for your product or service (presuming you're in the blogging space) than someone looking for something really generic. And because long-tail keywords tend to be more specific, it's usually easier to tell what people who search for those keywords are really looking for. Someone searching for the head term "blogging," on the other hand, could be searching it for a whole host of reasons unrelated to your business.
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
Forget whether or not to put your keyword in it, make it relevant to a searcher and write it for humans, not search engines. If you want to have this 20-word meta description which accurately describes the page you have optimised (for one or two keyword phrases) when people use Google to search, make sure the keyword is in there. There is more likelihood it will be used by Google as your snippet description in SERPs.
This is why developing a list of keywords is one of the first and most important steps in any search engine optimization initiative. Keywords and SEO are directly connected when it comes to running a winning search marketing campaign. Because keywords are foundational for all your other SEO efforts, it's well worth the time and investment to ensure your SEO keywords are highly relevant to your audience and effectively organized for action.