1 cc (cubic centimeter) is equal to 1 ml (milliliter), it measures the volume. For example if a bottle contains 10 ml of liquid, this corresponds to 10 ccs.
1 mg (milligram) measures the dose of a medication, 1 mg equals 1 / 1000 gram.
1 mcg (microgram) equals 1 / 1000 of milligram.
1 International Unit (IU) is also used to measure the dose of a preparation for the hormones, for example.