As no one has answered this yet, I’ll take a general stab at it. There are books on this subject and I’m sure there are websites, too, but I’m not that motivated to look them up! 
It’s not an “only one way to do it” type of process. the answers to all your questions are “yes.”
The bottom line is that it takes a lot of money to make a film and distribute it: it costs money for the film (or video) to shoot the film, for the equipment, including cameras, film, lights, power, sets, costumes, food, locations, rights, etc. etc. etc.
The most common way movies get made is through the movie studios. They have a lot of money. They can pay big bucks for the rights to works of literature or comic books that they think will make a popular movie. They can pay big bucks for writers to write and rewrite the scripts. They can pay producers to put together the project, casting agents to contact famous actors and producers to make the movie, and pay the millions to process the film, distribute it, advertise it, etc.
That being said, it is not the only way. Some production companies are successful enough that they can shell out the required money to get a movie made, and then sell the distribution rights to a studio. Sometimes a director or an actor will want to make a certain movie, and since they are successful enough that production companies or studios think that their involvement will lead to a money-making movie, the production companies or studios will fund their project.
Sometimes people involved in the industry will come across what they think is a good script, and then try to get it made. One way to do this is to show it to successfull actors or directors, and if they get them interested enough to “attach” themselves to the project, then they could maybe get production companies or studios to shell out the bucks.
At the other end of the spectrum, some would-be producers or directors just pull together all the money they can beg, borrow or steal and make a movie themselves on the cheap. Examples of this would be Robert Townsend using his credit cards to make his first movie, or Robert Rodriguez making his first film in Mxico for very little money. Once a showable final project is made, they can then bring it to film festivals or show it directly to production companies or distributors to try to get them to buy the distribution rights and pay the money to get it distributed and seen.
This is a very general answer to a very broad question, and it’s all the time I have for now. Maybe some others would like to chime in with more details.