Can you learn to play the piano by using a keyboard?

Of course! A keyboard is just a little smaller, but the concept is the same!

You can for the first year or two, but after that, save yourself some frustration and invest in a real piano. The keys of a piano feel and play a little differently, but there is no difference between the two in the way you would learn to play.

This site has many piano lessons and online piano lessons reviews, you can take a look.