What is the importance of web visitor statistics (metrics) in Digital Marketing?

In my opinion Time Spent on Site and Bounce rate ,

For measurement there is multiple services available like Google Analytics, Clicky , Mint , Web Trends etc...

Time spent on site and Bounce rate both tell same store , 

1) Your content is valueable to users

2) You are taregting Right users

Some time its happen you page title or content miss lead user so as soon he land on your site he will left site from1st page that increase Bounce rate 

But there is another thing maybe your content is good but your presentation and navigation is not good thats why user quickly left your site like after2 page views thats impact user time spent on site / time spent on page stats 

Other then these there are lot of things you can consider like User Country , Region , Borwser , OS , refral domain etc... 

The following are some of the important metrics that needs to be measured. 

1. Number of Visitors

2. Bounce Rate

3. Conversion Rate

4. Unique Vs Repeat Visitors

5. Engagement Metrics and Paths of Conversion 

There are a number of Tools that can be used to measure the metrics and you could start with Google Analytics and then move on to other advances tools to measure the metrics of interest. The Metrics will provide us with insights about our website, such as the  demographics of the visitors, the engagememt quotient of our content and in genral the quality of the trafffic to the website. These insights can be used effectively in our marketing/sales campaigns.