Cremation is simply a form of disposition. The crematable casket is placed in a cremation chamber where, through a process of heat and evaporation, the body is reduced to its original elements- bone fragments, not ashes.
Many families select an appropriate service to take place before the cremation or after. You may still have a traditional funeral with visitation, with the cremation disposition taking place after the service.
As specialized equipment and training is required for cremations, they typically occur at designated locations. Some funeral homes do have onsite cremation facilities. If you are planning on a cremation, ask where they actual cremation process will take place. Direct cremation usually means cremation with no visitation or services. Some people choose direct cremation believing that the quickest, simple option is best.