Captured packets can reveal a lot about your network traffic. In some cases, you can tell whether someone accessed a particular webpage by looking at the packets that traveled between your web browser and the server hosting that webpage. If you suspect that malware is attacking your system, you can look at captured packets to determine where that malware came from and what it did once inside your network.

•  It is easy to use, install, and configure.
•  It is compatible with most operating systems, including Windows, Linux, Mac OS X, and Unix.
•  It does not require special hardware.
•  It provides detailed packet information such as source IP address, destination IP address,  protocol type, etc.
•  It is available on almost every platform.
•  It supports several different protocols, including TCP/IP, UDP, ICMP, ARP, HTTP, FTP, SMTP, POP3, IMAP, SSH, Telnet, SNMP, SSL, SCTP, NNTP, LDAP, RDP, VNC, and more.

More info: What is User Datagram Protocol (UDP)