Final answer:
Meiosis is a type of cell division that produces gametes and reduces the chromosome number. It is necessary for sexual reproduction and genetic variation in offspring.
Step-by-step explanation:
Meiosis is a type of cell division that reduces the chromosome number by half and produces gametes. It involves two rounds of nuclear division, resulting in four genetically unique haploid cells. Meiosis is necessary because it allows organisms to produce haploid gametes, which are necessary for sexual reproduction and ensure genetic variation in offspring.