What is a UDP port?

Answer 1

In the TCP and UDP protocols used in computer networking, a port is a special number present in the header of a data packet. Ports are typically used to map data to a particular process running on a computer. As an example, a server used for sending and receiving email may provide both an SMTP and a POP3 service; these will be handled by different server processes, and the port number will be used to determine which data is associated with which process. This may be considered loosely analogous to simulating the effect of a single server with multiple physical connections. Note that not all transport layers use network ports; for example, although UDP and TCP use ports, ICMP does not.

Answer 2

Well that was the most meaningless answer I've seen in a while.
UDP is used to stream data with no error correction or response necessary. It's used for internet phone calls and internet radio and stuff.
With TCP/IP any errors get detected and the data gets resent. But you don't have time for that with Voice over IP or radio broadcasts, so they use UDP/IP instead.