Check the "Tips and Tricks" section of this forum. There are two articles on choosing hosting and getting your site started.

The short answer to your queries: No, they cannot offer unlimited hosting bandwidth or disk space. They simply make this claim knowing that most people are lucky to use a fraction of what they purchase in a shared hosting plan. If you read their terms of service, they may disclose this so that you cannot hold it against them if they cancel your service if you actually do exceed an "acceptable" amount of bandwidth and disk space. Try to find a hosting plan that will actually give you what they say they will give you.

Many people are confused about how much bandwidth and disk space they actually need. What type of website will you be running and how much traffic do you expect to have for the first year? Most small businesses are lucky to use 1GB of bandwidth and 3GB of disk space/month. Don't pay for what you will not be using (or evening in some cases what you won't be getting). If you know you will be needing a very large amount of bandwidth and disk space, I recommend that you look into Virtual Private Servers (VPS) or Dedicated Servers.

let me know if I can help answer any other questions,