A zygote would refer to a cell resulting from the process of fertilization. What happens is that, two haploid cells—typically an ovum coming from a female and the sperm cell coming from the male species—will merge, forming a diploid cell which is known as the zygote (also spelled as zygocyte).
In animals, the zygotes go through a series of mitotic cell divisions and then form an embryo. There are other organisms which may go through meiotic cell division at this point.
You might note that twins as well as multiple births could be either monozygotic (that is, identical) or dizygotic (that is, fraternal), which means they can arise from either one or more (that is, strictly, two) fertilisation events.
In animals, the zygotes go through a series of mitotic cell divisions and then form an embryo. There are other organisms which may go through meiotic cell division at this point.
You might note that twins as well as multiple births could be either monozygotic (that is, identical) or dizygotic (that is, fraternal), which means they can arise from either one or more (that is, strictly, two) fertilisation events.