I have read through the answers given so far, they are correct and true but some of the answers are not foundational and not basic. When you explain things to beginners, you try and use the beginners language even if you are an expert.
O_e_l_e_o is good at this and he has been helping me in the simplest method and language ever.

If you examine this question, you will understand that this question on its own is faulty, and trying to answer a faulty question will make the answers look non cogent even if they are.

First the OP, will have to understand that the correct question should be What is the difference between the Lightening Network and the Bitcoin Network.  And not the difference between LN and Bitcoin.
Bitcoin is a coin and LN is not. The comparison should be between the LN channel and the blockchain (or Bitcoin network).

So, OP the LN as others have said is a second layer of bitcoin network, which is introduced to fasten transaction and decongest the bitcoin network.
You and your friend can open  a Lightening Network channel, and the opening will be registered on the blockchain, every other transactions you do are off the blockchain until when you close the LN, and the summary transaction would be broadcasted in the bitcoin network. By this, you do not have to pay for the transaction fees which happened between you and your friend throughout the channel existed.