An haploid cell has 1 copy of her cromosomes, and a diploid has two copies of all her cromosomes.
A human has all his cells diploid, except the germinal cells (espermatozoids and oocits). In a human, the autosomic cell is diploid (all the body except gonades), and sexual (germinal) cell is haploid. Some organisms can be haploid during all their life like some fungi f.e. Humans and other mamals are diploid all their life except the germinal cells. And then, the majority of plants have complex cycles altering haploid and diploid periods.
