Photoshop functionality can be extended by add-on programs called Photoshop plugins (or plug-ins). Adobe creates some plugins, such as Adobe Camera Raw, but third-party companies develop most plugins, according to Adobe’s specifications. Some are free and some are commercial software. Most plugins work with only Photoshop or Photoshop-compatible hosts, but a few can also be run as standalone applications.
There are various types of plugins, such as filter, export, import, selection, color correction, and automation. The most popular plugins are the filter plugins (also known as a 8bfplugins), available under the Filter menu in Photoshop. Filter plugins can either modify the current image or create content. Below are some popular types of plugins, and some well-known companies associated with them:
Color correction plugins (Alien Skin Software, Nik Software, OnOne Software, Topaz Labs Software, The Plugin Site, etc.)
Special effects plugins (Alien Skin Software, Auto FX Software, AV Bros., Flaming Pear Software, etc.)
3D effects plugins (Andromeda Software, Strata, etc.)
Adobe Camera Raw (also known as ACR and Camera Raw) is a special plugin, supplied free by Adobe, used primarily to read and process raw image files so that the resultant images can be processed by Photoshop. It can also be used from within Adobe Bridge.