Constructors main purpose

Constructors are designed to assign parameters to properties or fields. But why constructors are used sometimes in cases where normal methods can be used?

public SpeedUp()

    {
      Speed+=5;
    }

The difference between a constructor and a method:

A constructor runs automatically, its the first method to run when you create a new instance of a class.
It will only run once.

A method has to be called in order for it to run and can be called and run as many times as you would like

Hope this helps