A reproduction of a painting is a copy of the original that looks just like it. The act of reproduction involves making copies or having babies.
We won't get into the birds and the bees, but reproduction is the sexual activity of producing offspring, also known as procreation. But reproduction isn't just the act of making babies. It can involve making copies or replications. Similarly, a reproduction is an identical version of something, often artwork. There are many reproductions of Picasso's paintings but in every case, there is only one original and it's worth far more than all the copies combined.