There are many factors which are used to determine the relevancy of the website.
Domain age: older is better.
Keyword competition: It is the measure of how difficult it will be to rank for a particular keyword. The competition for a keyword can vary depending on how popular the keyword is and competition of using the same keyword in other websites.
Back links: The more links a page gets, the better. Links from domains with a high authority are more valuable.
Update frequency: Frequently updating Web Pages or posting articles has a positive effect.