I'm new at this stuff. I see abbreviations in vendor's sheets and I dunno what they mean? like these:

This is the detail of the content of a product on sale which apparently is a character morph with skin textures. This allows you to change the body and face of the base character for which it is designed (INJ) MATS are to be applied to change the color and texture of skin, eyes, lips separately etc. The INJs are in the Pose part of the pose library, the MATs in the Material part.

MAT files can be found under the Pose category in many older content files before P13.  Make sure that when purchasing skin textures, body morphs, or makeup sets, they match the model you want to use them on.  There is no 'one fits all' solution.  For example, if the set is designed for Victoria 4, make sure you will be using it for Victoria 4.

ah, thanks all.

Being more specific on meanings: 

-INJ: injects a morph/shape.

-REM: removes a morph/shape.

-MAT: applies a material. 

For older Poser products, all of those were in the Pose section of your library, but the material section came later, I think in Poser 5? Some vendors still create material poses, but for store purposes they require materials to be in the material section nowadays :)