This question was asked several times through askphysics, but I was thinking whether or not to answer such a simple question. But when I pondered, I felt that there is something which I can tell the world through the answer to this post.
If you search, you can find several definitions to “Machine”
To be quite simple, A machine is any device which makes human efforts easier. It may be used to magnify human capabilities, physical or psychological. It may be partially or completely automated.
A machine is helpful to save human effort, not energy. There are even cases where the machine is not providing any mechanical gain of effort, but changes its direction so that the effort can be conveniently applied.
As per COLLIN’S DICTIONARY