What is the use of alexa?

[Gowtham20]

Alexa Traffic can be used as a competitive intelligence tool but you should take into consideration the fact that its sample size of audience is too small; Just enter your competitor's site in the "Compare Sites" section and measure the results of your web marketing efforts in comparison with your competitors'.

As opposed to Google's PageRank, the lower your ranking number, the better.
It helps Webmasters and advertisers see the true marketing potential of your Web site. The better your Alexa rank, the higher they will be willing to bid to buy advertising space on your Web site.