Foetus is an unborn baby that develops and grows inside the uterus. The developing embryo gradually differentiates into different body parts, such as hands, legs, head and other. Thus, when in the embryo different body parts can be identified, it is called a foetus.

The zygote is a fertilized egg that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm). This process is known as fertilization. A zygote is further developed into an embryo. A zygote is a haploid cell. The zygote begins as a single cell but divides rapidly in the days following fertilization.

Fertilisation results in the formation of zygote which begins to develop into an embryo. The zygote divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is termed an embryo. The embryo gets embedded in the wall of the uterus for further development.

Budding is a type of asexual reproduction in which a small outgrowth known as a bud protrudes out from the parent body which detached on maturity and develops as a new organism. Hydra reproduces by budding.