The importance of a good SEO strategy

SEO if implemented correctly will let you know how many unique  visitors, how many repeat visitors and referral traffic your site is getting.

• Unique Visitors – This is the total number of  individual visitors  that have visited your site in a specified period  of time. This doesn’t  include repeat visitors, resulting in an accurate  assessment of how  popular your content is. This tells you how well  your campaign is  driving visitors to your site.
   
• Repeat Visitors  – This tells you how many visitors have visited your  site more than  once. This tells you how attractive and resourceful your  content is if  people think enough of it to come back. If you don’t have  enough repeat  visitors, you need to add more valuable content worthy of  a repeat  visit.
   
• Referral Traffic – These are non-search engines sites  that send  traffic to your site. How do you attain more of these?  Inbound links!  Start featuring attractive and resourceful content that  others share on  their own site or blog.

Using SEO to  measure these metrics will let you know what parts of your website are  working and which ones aren't so you can make the changes accordingly.

Source: www.quora.com