While HostGator is fairly generous compared to other providers, the catch with the "unlimited" shared hosting plans are as follows:
1. They'll cut you off if your site is taking up more than 25% of the CPU for more that 90 seconds at a time.
2. Your site cannot take up more than 25% of the server's RAM for longer than 90 seconds at a time.
3. Hostgator limits how many processes (number of running scripts) you can have running on the server at a time (limit is 25 on shared hosting).
4. Hostgator limits the number of files you can host to 250,000 or so.
5. A process may not run for longer than ten minutes.
6. MySQL queries cannot run for longer than 15 seconds.
But other than that, sure, the bandwidth is unlimited. The main catch is that since bandwidth is directly tied to CPU usage and RAM, the term "unlimited" is questionable. It's unlimited as long as you're not using too much CPU/RAM at a time for longer than 90 seconds at a time. To get an idea of "too much" see
Hostgator's Server Specs:
Our shared servers have dual Xeon E5520 2.26 GHz Quad Core Processors. We run CentOS 5.5 Enterprise Linux x86. The servers have 12 GB of DDR2 or DDR3 RAM. The connection speed on our servers is 100 mbps (mega bits per second). We also have RAID10 and instant weekly backups of your content. Our data center is SoftLayer located in Dallas, Texas, USA.
You cannot use more than 25% of the CPU/RAM resources for longer than 90 seconds.
This is all outlined in HostGator's
Terms of Service. Always read through the Terms of Service carefully before signing up to a provider. They usually hide the limits somewhere in the middle of the document.