Website setting is important because in your website settings you set the keywords and description for your website. 
Those two are very important factors in SEO and have also further meaning relating to Search Engine Results Page (SERPs). 

Meta Description

The desctiption of the website plays an ambiguous role:
1. The website description can serve as an area where you push keywords to help index your website. When writing a description choose the most valuable keywords for your website and insert them a couple of time into your description
2. The description on some search engines (as Google) is what will be shown as the description in the SERPs (Search engine results pages). A good description is many times a call to action to click the website link and enter the website (getting traffic).

Meta Keywords

Meta keywords are mostly a list of 5-10 keywords describing the content of your website. The Meta keywords will appear on each and every page of your website. That is why not every website needs Meta keywords for the whole website. That is because on a big website with lots of pages each page should have keywords inserted in it - to crawl that specific page. By adding meta keywords to existing exising keywords of the page, it would create un-neccesary stuffing  (Which will look bad on search engines). That is why mostly if you have a website of more the 15 pages then sometimes you don't need Meta keywords and you can just add page keywords instead.

On the other hand if you have got a small website adding a Meta keywords to the whole site can save you the time of going to each page. That way you can add keywords just once for the whole website.