How the insert() function in STL containers works

I am trying to make my own versions of the STL containers (for practice in C++) and I do not fully understand how the insert function works. I understand how to properly call and use the function, but I do not comprehend how to implement my own version of the function. How exactly does the insert function work under the hood. I am referring to the instances of the insert function that take an iterator as one of their parameters.