There are lots of different ways they make it to the cinema:
1. An idea
Who has it? Could be a writer a director or someone like you!
2. The pitch
A studio has to be convinced that the film is worth making. Someone has to talk them in to it. To get the idea across it will normally be developed into a summary of how the film will go.
3. The studio
They put together the team to make the movie. Once a director has been picked they find actors, and the studio also finds the money. Sometimes a studio needs to find investors to raise enough cash.
The location scouts must find the places to film the movie, then it's ready to be made. It is not filmed in the order you see it on screen. The director has a storyboard and what they film first depends on which actors and locations are available.
The raw filming (called rushes) is edited in this stage. The music is added and sometimes actors re-record lines that weren't clear enough.
Editing is mostly done on computers. In the past, film was actually cut into bits and stuck back together - movie people still say an edited film has been 'cut'.
The film is sent out to cinemas ready for you to see it.