Its difficult to differentiate between a sprain and a strain.
A sprain occurs at a joint and involves ligaments most commonly a sprained ankle.
A strain is an injury to muscle or tendons and tends to occur when the muscle is stretched for instance when playing sport.
Luckily the initial treatment for both injuries is the same the RICE procedure:
Rest the injured part Ice apply ice or a cold pad to the injured area Comfortably support the injury using a bandage or soft padding Elevate the injured part