Computer science is an implementation of mathematicians, scientist and engineers. A mathematics which use origins of the computer science and provide logic. Science provide process for learning and refinement and Engineering provide approach to build hardware and software.
Computer science theory field is concerning about the limits of computation. Majorly it includes how fast certain problem is solved some make very less time and some are very time taking and impossible to figure out. It also includes machine learning, developing new algorithms.
It all about design which lies in the realm of engineering and chip architecture but also electrical design such as building circuits and chips.
This field cover topics with the device interconnection which is related to systems. It also includes some of the practical topics like resources sharing, and creating better protocol to transmitting data which reduce network traffic. Other work it include is peer to peer network which allow resource detection and load balancing to prevent damaging the network.
This field is all about designing and making animated movies, but also cover topics like data visualization. There are some of the graphics which contain 2D and 3D world.
This field is the heart of computer science all the non-theory areas depend on programming language. It includes optimization means to speed up your program and these days compiler optimization do amazing things.
This field relies on some of the work of programming language and deals with the design and implementation of software. It covers topic like defensive programming, focus on designing and work on large-scale projects.