Capturing will take packets from a network adapter, and save them to a file
on your harddisk.
To hide all the lowlevel machine dependent details from
Wireshark, the libpcap/WinPcap (see Section 5.9, “libpcap/WinPcap (optional)”) library
is used. This library provides a general purpose interface to capture
packets from a lot of different network interface types (Ethernet,
Token Ring, ...).