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
Now, never because I no longer keep people like that in my life.