What does ‘enterprise Linux’ actually mean? Not asking snarkily; I’m curious what the main differences are between this and other Linux distros. Is it mostly about getting good tech support?

If you have more than a 100 linux machines you certainly need someone who knows linux to support them. You can either hire a team to do this or hire someone who will manage a support contract with suse/ubuntu/red hat etc.

Yeah it's about support contracts, which covers a lot of services actually such as maintaining security audited package repositories. But most importantly it's about support life cycles you can rely on for a long term investment of time and infrastructure outlays.

For example, RHEL 10 has a planned support phase out until 2035, with extended support available until 2038.

They do tend to have a different goal for their intial installation and configuration to consumer distros, with a focus on security and providing tools you will need in an enterprise hosting environment.

SLAs, support, LTS services etc...