Systematic refers to something being put into a system. Systematic theology is, therefore, the division of theology into systems that explain its various areas. For example, many books of the Bible give information about the angels. No one book gives all the information about the angels. Systematic theology takes all the information about angels from all the books of the Bible and organizes it into a system called angelology. That is what systematic theology is all aboutorganizing the teachings of the Bible into categorical systems.
In addition to systematic theology, there are other ways that theology can be divided. Biblical theology is the study of a certain book (or books) of the Bible and emphasizing the different aspects of theology it focuses on. For example, the Gospel of John is very Christological since it focuses so much on the deity of Christ (John 1:1, 14; 8:58; 10:30; 20:28). Historical theology is the study of doctrines and how they have developed over the centuries of the Christian church. Dogmatic theology is the study of the doctrines of certain Christian groups that have systematized doctrinefor example, Calvinistic theology and dispensational theology. Contemporary theology is the study of doctrines that have developed or come into focus in recent times. No matter what method of theology is studied, what is important is that theology is studied.