A correlation is a single numerical value that is used to describe the relationship between two variables. All correlations have strength and direction. When two variables have a positive correlation, that means the two variables move in the same direction. The closer a positive correlation is to 1, the stronger it is.
William Gilbert discovered electricity, not Nikola Tesla. Nikola Tesla invented things. not discovered electricity. Again, William Gilbert discovered it and named it. He did this in the 1600s. It wasn't Nikola Tesla.
Tesla based his wireless electricity idea on a concept known as electromagnetic induction, which was discovered by Michael Faraday in 1831 and holds that electric current flowing through one wire can induce current to flow in another wire, nearby.