Het (short for heterozygous) means an animal carries one copy of a recessive gene without visually showing it — so a "het albino" looks normal but can pass albino on to its offspring.
Het status matters for breeding, not care: a het animal is cared for exactly like a normal one. "100% het" is guaranteed by parentage; "66% het" or "poss. het" is a probability, so buy from honest, well-documented sources.