Man made things are not always safe and pure.but natural things can be purified in well refined manner Man made things may be less in value but natural things are mostly high in value. Natural things are necessary for survival but there's no such necessity in man made things. Natural things mostly are limited resources where as man can make number of things.
A man-made resource is a resource that has been created through the acts of humans and simply language we can say things made by man are called man made things. For example, bleach is a man-made resource. It does not exist in nature (in any significant quantity), and is produced and consumed by humans.

A natural resource is a resource that exists naturally. It might also be defined as a resource which man did not create (i.e. not man-made). For example, coal is a natural resource. It only exists in nature, and it is consumed by humans.