There are four major areas in the study of ordinary differential equations that are of interest in pure and applied science.
Of these four areas, the study of exact solutions has the longest history, dating back to the period just after the discovery of calculus by Sir Isaac Newton and Gottfried Wilhelm von Leibniz. The following table is given as an introduction to the types of equations that can be solved by
DSolve.
Examples of ODEs belonging to each of these types are given in other tutorials (clicking a link in the table will bring up the relevant examples).