Public key encryption I am not getting whole idea behind Public Key Encryption technique.

As according to fact, public key encryption method uses two keys a public key known to everyone private key known only to recipient of the message

For an instance let assume, John wants to send a secure message to Jane, He uses Jane's public key to encrypt the message. Jane then uses her private key to decrypt it.

The thing i am not getting is, as far as i know if we want to encrypt any message using a key, from that same key only we can decrypt that particular message.

But in public key encryption case both keys are different than how it is possible to decrypt the message.

Please clarify my issue and guide me through if i am going anywhere wrong in understanding the whole concept
Here is a great video which shows principles for public key cryptography using colors, which makes it easy to understand for everyone:
https://www.youtube.com/watch?v=YEBfamv-_do

Now what you missed is that it is possible to generate a secret key, and give away something which enables encryption but not decryption. This is the principle of public key encryption.