Computer sciences is mathematics, software engineering is programming, IT support (I’m including infrastructure and infosec here) is making sure that computers run fine for the employees needs.

Generally, but I am likely missing some stuff:

Computer Science: The underlying theory around making efficient computer software (I would consider the hardware side computer engineering)

Information Technology: the process of managing computer software and hardware systems for an organization

Software Engineering: the process of developing software including writing code, prioritizing features / bug fixes

Tech Support: part of IT. Troubleshooting and resolving issues with an organizations hardware and software systems