Depends how you set it up.
(I'll caveat below by saying that when I talk about 'enterprise', we're talking about >500 employees and hundreds of millions in revenue annually.)
In many cases, they'll have their environment set up with standard *nix and Windows SOEs. You'll work with their admins to configure your software, and you'll direct them how to integrate it into their environment (DNS, etc). You'll need to think about backups, security, access management, and how all of this will integrate with their existing requirements.
Support arrangements differ, for example if you have an SQL DB underneath your software they might want it on their standard image, in which case you'll have to deploy and configure your software accordingly. Typically, they'll be responsible for the maintenance of the platforms, and you'll be the support for the software. No enterprise will simply deploy a VM image you hand to them (unless you're Oracle or MS).
You'll also have to provide other support materials, so their helpdesk can support their end-users.
As others have mentioned, you'll be agreeing to SLAs with them (eg a Priority 1 incident will need immediate phone support, P2 incidents need acknowledgement within 24 hours, and so on). You'll be issuing a yearly invoice most likely.
You'll have to agree to their standard IT services contract, and because you're a small vendor you probably won't get much say in the way of changes. Depending on how large your contract is (north of ~$50-100k perhaps?), you'll need to make sure you can comply with any of their insurance requirements (things like public liability, etc). You might also have to demonstrate financial stability, both historically, and into the future (with a business strategy, plans, etc)
TLDR: Enterprise companies can seem super hardcore about this if you're used to dealing with small shops.