Clones are genetic copies of cells or organisms. Currently, we have clones for bacteria, viruses, plants, human cells (not human beings) and some animals (e.g. frogs, sheep, buffalo, horse, cat, monkey).
For bacteria and viruses, cloning is very useful to scientists in the study of these organisms, i.e. how they multiply, change, cause disease, etc. With these we can test drugs on these cells with the aim of controlling them.
Cloning in plants is mainly to hasten the reproductive cycle (faster food production) and to select for good traits e.g. juicier, sweeter, drought resistant, pest resistant, etc.
For animal/human cells, cloning is used in treatment/management of diseases. In this case, they take an egg then remove the nucleus. A nucleus from a body cell (somatic cell) is then inserted into the egg. This enables the egg to develop into any type of cell (stem cell) that we want, e.g. cells of the skin, eye, bone, immune system, etc. This is useful in study of animal/human development and also treatment of disease such as Alzheimer’s, diabetes, Leukemia, etc. NO HUMAN HAS BEEN CLONED. That only happens in movies. In fact, many of the animals cloned do not live very long with some dying just days after birth.
You should know that cloning of human cells is very controlled. Not any scientist can do it. You must get approval from scientific boards and explain what it is for and if allowed, it will be monitored! Currently at KEMRI-Wellcome Trust Kilifi, we have no cloning experiments here.
Read more about cloning and how it is helping scientists learn about cells and organisms with the aim of clearing diseases and increasing food production. It is indeed fantastic science.