I'm probably not 100% right about this, but my understanding is that CS generally incorporates Programming, Systems Engineering, Server Admin, Database Admin and things of that nature ...
IT usually incorporates non-programming but computer related positions like Helpdesk Operator, Network Admin, Desktop Support, and things like that ... CS people can often fall under the IT category but not all IT people could be considered CS people ...
It also really depends on the company. I've worked for 3 different companies (2 different ones during my undergrad, and 2 different divisions at one job). Every company had their people structured differently, and restructuing is very common.
In any case, if you want to do strictly programming or something CS related, then you're limiting your job options a bit. If you get a really well rounded education while at college (I highly recommend working for your school's IT department or working somewhere computer related during your undergrad) then you can work a wide range of jobs and also figure out what your specialty is and what you prefer to do. Personally I prefer doing IT work like networking, or desktop support over programming but I also really like doing UNIX admin work. So when I went for interviews I could tell people what my interests and what my specialties were.
You shouldn't worry about selecting a specialty or what your preference is right now if you're a freshman or soon-to-be freshman... You'll figure it out as you go along and take different classes and/or work different jobs.