With a shared hosting plan, you are renting space on a server that you share with other website owners. This also means you're sharing resources like bandwidth, memory, and processing power. This can be a problem, because a web host company typically supports hundreds, even thousands, of websites on a single server. Most of these websites will get very little traffic, allowing those who do see higher levels of traffic to use the resources they need. Nevertheless, there are no guarantees that you will get the resources necessary to support your website.
Many services offer a low "starting price," but require you to prepay for two or three years of service to get that price. After the promotional period, the renewal price for some services can be two, three, or even four times the initial promotional pricing. While the initial deal might be incredible, the cost of transferring your site (or paying the added fee) in a couple of years may be something to consider.