The guy first gives the definition of differential equations. He explains that a differential equation is an equation that contains the derivatives of an unknown function. He then gives some examples of differential equation and explains what the equation's order means. After that he gives an example on how to solve a simple equation. He calculates it and gives examples of graphs. Then he explains what a general solution is and how to narrow down the number of solutions using data from the problem. He shows how to find C (the constant number). In the end he makes a summary of the video presenting the 2 types of solutions - general and particular.