INJ/REM poses are a way to keep the figures as small as possible. You can INJect morphs or REMove morphs with these. These are used mainly by DAZ and the Mil figures like Victoria 3, Michael 3, David, etc. One note, what oilscum said about placement of the INJ/REM poses used to be true. With the newer figures, and with the current version of Victoria 3 it is no longer necessary to keep them in the main runtime. This is true with Windows anyway, don't know about Mac.