If the returns on two stocks are highly correlated, what does this mean? If they have no

Question:

If the returns on two are highly correlated, what does this mean? If they have no correlation? If they are negatively correlated?

Stocks
Stocks or shares are generally equity instruments that provide the largest source of raising funds in any public or private listed company's. The instruments are issued on a stock exchange from where a large number of general public who are willing...