Three things we monitor and so does Google is your internal links ( onsite page to page links ), external links ( links from your website to somebody elses ), and backlinks ( links pointing at your website from somebody else`s website ).
All three can and do effect your S.E.R.P. ( search engine results page ) positioning. If Google can`t find them then they can`t index them or find them useful for those whom have a query about that topic. This inturn will produce what is known as a "404 status - URL not found on this server" most generally if for some reason the user can`t access the page. And if a user can`t access the page that means they will more than likely leave your website and heading to someone else`s. If your website is something more than just a blog such as a service or an online store this could mean a loss of sales and more. It is as though you placed a locked door infront of your customers.
This can be just as bothersome to individuals coming to your website and you have affiliate links and links to other websites for resources or cross vendors. Visitors came to your website with an intent to read or buy your product(s) and or service(s).
You have other website owners and merchants who link to you as a resource of sorts for your product(s) and or service(s) as backlinks. They like what you are saying, doing, and or selling and want others to know. In normal non-internet life we would refer by word of mouth, "WOM", but on the internet this is either a backlink, "organic link", or an affiliate link, "for profit link" usually acompanied with some sort of creative.
As you grow in your knowledge of running a business on the internet you will learn about Google`s algorithms known as the "Panda algorithm and Penguin algorithm" and how Google monitors all of your links and how they effect your search engine results page position which also defines your domain authority, page authority, and linkability overall.