(Context for my answer: I’m a layperson who has read a lot about Holochain, not a programmer, so take it with a grain of salt)
First of all, though you could say Holochain is a superset of blockchain, I don’t think that necessarily means you can draw direct parallels between how Ethereum smart contracts work and how Holochain works. That being said, I’ll try to answer your questions from my understanding:
- A group of people running a hApp together is sort of like deploying a smart contract. Note there is no one single Holochain, so nothing is deployed on “the Holochain,” as every hApp is its own private network
- Each node holds the DNA of the hApp as the first entry in their source chain, which perhaps you could draw a parallel with the “contract address where the code is stored”
- hApps have “zome” functions that define what the hApp can do, which can be all sorts of things, including transactions
- Do you mean between two different hApps? I’m not 100% sure, but I believe this would be done with a bridge. See https://developer.holochain.org/docs/concepts/8_calls_capabilities/
On that note, if you haven’t already, I would suggest taking a look at the core concepts section of the developer website. As you do so, it may help to put aside what you know about how Ethereum works and just approach Holochain as a completely new thing with a totally different design.