The most common application is e-mail.
Modems are about communications standards.
In the case of the newer 56K modems, the same is true only more so. 56K modems came on the market two years ago, with two competing, incompatible communications standards. Now all 56K modems must bear this standard, so if you're shopping, make sure you see this designation. It is called V.34, and it has been revised and improved upon several times during its lifetime. However, regardless of which type of modem or its communications standards, there is always the chance that a bug will be found or an improvement made.