Omni protocol. Would appreciate your insight. Thanks.

I have a burning question regarding the Omni protocol and I'm a little lost where to find the answer so any help would be appreciated. Let me see if I can word my question correctly. First off, I trust I'm in the correct forum. Please excuse me if I'm not.

Question: omni as I understand it is a protocol that runs on top of the bitcoin blockchain. Like http over TCP/IP I believe. I understand how bitcoin transactions get written into the blockchain after verification of inputs, outputs, ownership, hash etc. But I'm unsure of what gets written into the bitcoin blockchain using the Omni protocol? I believe Mastercoin, Tether, Maid make use of Omni to write to the bitcoin blockchain. What does the transaction look like? Are the transactions still using the bitcoin addresses? Are there bitcoin inputs and outputs? Does the currency that uses the Omni protocol create a transaction using the bitcoin fields diffently? Any help would be appreciated. Thanks in advance.