what are haploid cells? how and when do cells gain such a condition?

A cell is haploid if it contains exactly half of a species typical full set of genetic material. Haploid cells are often used in sexual reproduction.

Most cells within humans (and other animals) are diploid, which means they have two copies of each chromosome. Sex cells, however, are haploid – they have only one copy of each chromosome. Haploid cells in animals are formed through meiosis. In sexual reproduction, haploid cells come together to make a diploid organism.