する verbs are one of only two verbs in Japanese that do not follow the standard rules of conjugation for Godan and Ichidan verbs. The other primary verb being 来（く）る. する means to do something, or to make something a certain way.

• 洗濯（せんたく）をする。
  To do laundry.
• 料理（りょうり）をする。
  To cook. (Literally ‘to do food’)

する will almost always have the particle を attached to the thing that is being done (depending on the form of the verb). The reason that する verbs are called さ-column irregular conjugation verbs in Japanese is because the る in する does not conjugate, but is dropped.
This will leave す to be the part that conjugates. Because of this, する has qualities of both る-Verbs (the る being dropped), and う-Verbs (the remaining す changing, depending on the conjugation). Here are some examples of how する changes.
（さ）せる, （し）ます, （す）る, （せ）よ
We will learn more about each of these conjugations of する, and their individual meanings at a later stage. For now, let’s take a look at the polite します conjugation.

• 電話（でんわ）をします。
  To make a call.
• 勉強（べんきょう）をします。
  To study.

In a broader sense, する can be thought of as meaning ‘to do something that has an external effect’.