Alexa rank is a good way for people to check what kind of traffic a site is having and also how popular a site is (more or less) even if the result is not correct. Some adnetworks like Snoork Ads allow only site with alexa better than 1 000 000(?, sorry I don't remember the exact number) and it's really easy to get.
When you have copy/pasted the alexa code on your website or blog, you need visits. Alexa ranking is based on amount of visitors and amount of visits (refreshes). That means that one person can visit your website (you) and refresh it several times and each time your site will be refreshed, alexa will improve.
The method above won't get you huge results and that's why I recommend this traffic method instead. Go and use traffic exchanges! Traffic exchange websites is a place where you visit websites and in return people will visit your website. It takes time but it's free! If you are too lazy you can buy very cheap traffic at ptc sites like pplinx, earneasycash and first5clicks. These ptc sites sell 1000 hits for 0.5-0.6$(Look at the zero in the beginning! It's almost free!).
Thank you for reading and don't forget to follow this blog for more updates and guides!