What is the physical meaning of critical points in black hole thermodynamic topics?

Question

In black hole thermodynamic topics, the critical points sometimes calculate. They are introduced in different types and calculated in conventional forms. Recently, in thermodynamic calculations, these critical points have been categorized into zero, first, and second-order phase transitions. I wanted to fully understand the physical concept of these critical points and phase transition. In fact, what is the main reason for the calculations of these critical points, what is the physical meaning, and what will be the application after the calculation