Plug-ins
Plug-ins are programs downloaded through Winamp that – when active – modify, provide visual embellishment, or alter the quality of a given audio track. There are five types of plug-ins: DSP/Effect, General Purpose, Input, Output, Visualization.
DSP/Effect
These plug-ins combine audio and visual effects. For example, the iZotope Vinyl plug-in is a digital DJ table. The graphic element is completely clickable. All the dials turn and as they turn, the sound of the playing track changes. This particular plug-in includes sound effects such as "scratch," "dust," "wear," and "noise." These all produce sounds similar to a DJ mixing records. This is a small image of the player:

General Purpose
This category covers a wide range of plug-in types, from programs that allow remote control of the Winamp Player to minibrowsers that stream music based on the genres of songs already downloaded in your Winamp files.
Input
Input plug-ins extend Winamp capabilities. They provide access to MPEG movies, audio files not supported by standard Winamp and other multimedia.
Output
Output plug-ins let you alter and modify the sounds played through your Winamp Player. For example, some output plug-ins let you record tracks with effects like crossfading -- a great tool for DJs.
Visualization
Visualization plug-ins provide dynamic graphic accompaniment, in syncopation with the selected track.
Skins
Skins are graphic face plates that replace the standard Winamp face plates for the Player, Equalizer and Playlist. The functionality of the keys and commands remain the same, the only difference between skins is the graphic presentation.