Most of this activity happens on Linux-based receivers like Enigma2 boxes. You can install different "emulators" (emus) like mgcamd , evocamd , or OSCam , each of which handles key files slightly differently.
The itself is a small text file or database containing a set of encrypted keys (usually in Hexadecimal format). These keys act like a temporary "password" that tells the Softcam how to decrypt a specific channel or provider's signal at a specific time. Softcam Key