All black holes are formed from the gravitational collapse of a star, usually having a great, massive, core. A star is created when huge, gigantic, gas clouds bind together due to attractive forces and form a hot core, combined from all the energy of the two gas clouds. This energy produced is so great when it first collides, that a nuclear reaction occurs and the gases within the star start to burn continuously. The Hydrogen gas is usually the first type of gas consumed in a star and then other gas elements such as Carbon, Oxygen, and Helium are consumed. This chain reaction fuels the star for millions or billions of years depending upon the amount of gases there.

The star manages to avoid collapsing at this point because of the equilibrium achieved by itself. The gravitational pull from the core of the star is equal to the gravitational pull of the gases forming a type of orbit, however when this equality is broken the star can go into several different stages. Usually if the star is small in mass, most of the gases will be consumed while some of it escapes. This occurs because there is not a tremendous gravitational pull upon those gases and therefore the star weakens and becomes smaller. It is then referred to as a White Dwarf.

In the event that the star possessed a greater mass, there is a potential for it to undergo a Supernova phenomenon, where the internal nuclear fusion processes escalate uncontrollably, resulting in a massive explosion of the star. After exploding a fraction of the star is usually left (if it has not turned into pure gas) and that fraction of the star is known as a neutron star. A black hole is one of the last option that a star may take. If the core of the star is so massive (approximately 6-8 solar masses; one solar mass being equal to the sun’s mass) then it is most likely that when the star’s gases are almost consumed those gases will collapse inward, forced into the core by the gravitational force laid upon them. After a black hole is created, the gravitational force continues to pull in space debris and other type of matters to help add to the mass of the core, making the hole stronger and more powerful.

Please follow the below links for previous chapters :-
Chapter 1 - Revealing the secrets of Black Hole
Chapter 2 - Observational history of Black Holes
Chapter 3 - If falling into a Black Hole
Chapter 4 - Death by spaghettification of Black Hole
Chapter 5 - Mystery of Monster Black Holes
Chapter 6 - Crossing a wormhole : Reality Or Science fiction
Chapter 7 - Unveiling the Secrets of Biggest Black Hole
Chapter 8 - Gravity Grasp - Exploring Time Dilation Near Black Holes