Replication doubts

Hi Replication Experts,

Can anyone explain in simple terms regarding my below doubts. I am very much confused with replication concepts.
I understand transactional replication is uni-directional i.e. changes from Publisher are moved to Subscriber and not vice versa.

1. what is the difference between Transactional replication and Peer to Peer replication? Is Peer to Peer replication is another form of Txnl replication?
2. What is the difference between transactional with updatable subscribers and Peer to peer replication?
3. What is the difference between Peer to Peer replication and Merge replication?

I am looking for simple answers so that once I understand basic things, I can drill down more.

Thank you.