LTE is a new form of wireless broadband. It is primarily for handheld devices and supports roaming on cell phones and PDAs and such. It is understood to be a fourth generation technology (along with Wimax) because it moves beyond what is the norm in cellular communications.
It is heavily built/developed around internet protocol (IP), as such it has been intended to significantly better the process of web browsing, VoIP and other IP services. It has been designed to allow downloading up to 300mbps or higher. In actual practice it can be expected to be lower.
It is an R&D at this point and not expected to be released for quite some time.