Cornflour is also known as corn starch. It is only the starch obtained from the corn and is usually used in cooking to thicken or as a binding agent. Corn meal is flour that is obtained from grinding whole corn kernels and it is also known as maize flour or makke ka atta.
Main difference is texture..corn flour is a very fine powder where as corn meal is a coarse powder.
Corn flour is easily available. Corn meal is almost like your makki ka atta..just a little more coarse, you can get it made at your local chakki if that's possible