Internal links are those links which operate within your website, organising its pages for the easy navigation of users and search engines.
Internal linking helps create a website’s site map; the map which Google uses to ‘see’ the structure of a site. This allows Google to locate each page.
Internal links can bet set via anchor text (that text which users click on to access the link) which uses the relevant keywords for that page. This will add relevance and help Google to see what the page is about.
Also, in having a page linked to from the website’s homepage it will be given more weight and importance. However, Google does not recommend that all links should be from the homepage only as this will diffuse the weight of each individual link.
Instead, it is recommended that each page contains links to other pages via key phrases
