A short URL is not a web page on its own. Instead it is simply a pointer that forwards traffic to a different address. Effectively making the same web page available under more than one address - both the original (long address) and the bitcaly.com address. Browsers and servers talk back and forth using "headers" which contain various information. And a status code is one piece of information exchanged through a header. Let's say you click on a shortened URL ( eg.https://bitcaly.com/ygr ). A conversation through the use of headers will take place between your computer and the https://bitcaly.com server. bitcaly.com URLs use 301 redirects, which means your browser request will be responded to with a 301 = page moved permanently status code and will forward your browser to this "moved to" address (which we are calling the long URL). A search engine spider can follow links just as your browser did and is satisfied if it sees the 301 redirect method in-use. Search engines care about redirects because when they see one, they need to decide how to pass link popularity.
Uses and purposes:
Track user clicks from your site to external websites.
Share links inside email messages without breaking lines
Track email marketing campaigns with stats in all links
Share short links in Twitter messages, blogs, microblogs and other social networks
Create customized links to easily remember your favorite addresses (see useful examples)
Share short links in instant-messaging
Share easy-to-type links in news and printed material
Have clean and compact urls for your use
Hide real URL (user will see the real link only after clicking the short url)
Hide affiliate URLs
Create human-readable links
Send SMS messages with short links
Avoid errors when typing long urls links with parameters
Surprise users by creating links like this: https://bitcaly.com/you