hmm….there are hell LOT of things inside Computer Science. It will take days to discuss all of them. Here are some of the domains of CS:
Programming: inside programming you can have lots and lots of languages. You can divide into application pgming and System pgming. Application pgming are like java .net php etc. System pgming is mostly done with C and CPP.
Data Mining: Working with Big Data sets, data here are in GBs dn TBs to retrieve information from it. Databases are small portion of this really Big domain.
Networking: How internet works and how you are able to post your que here? how your cellphone get msgs/calls etc. Wired and Wireless networks. They have something called protocols which makes them work. Then Security in network itself is a huge domain to work in.
Security: Security again is divided: Network security and data security. Data sec includes cryptography stuffs, while network security is to make connection secure. There is Web Security which deals with securing web applications. Penetration testing: making websites free from attack risks.
Image Processing and multimedia: Dealing with multimedia stuffs, making big thins small by compression. Video and image formats like jpeg, avi, mkv etc.