I was wondering if anyone could explain to me what are weighted keys and non weighted keys on a keyboard. Thanks.

Synths and electronic pianos only require a very light touch to 'trigger' the note. Weighted keys are an attempt to simulate the touch and feel of a real piano. In the early days of electronc keyboards, many piano players complained that the keyboard didn't have enough resistance and didn't feel at all like a piano. The manufacturers added weights and springs so the keys took more effort to play and better simulated a piano. This enabled professional players to buy an electronic piano for the apartment or home and keep their hands in shape for when they played a real piano.
I hope this helps

Also you will find the more expensive electric pianos have keys that allow the piano to play louder when you hit the key harder, This also is part of it. That is why often someone that always plays on a cheaper keyboard has a harder time when they try to play a real piano or a better electric one