One of the easiest plots to understand is where the protagonist has to overcome a threat posed by the antagonist. Stories like the Harry Potter books, Star Wars: A New Hope and the James Bond films all revolve around this premise.
The plots in these types of stories threaten the status quo, and it falls to the protagonist and their companions to try and return their world back to the status quo. Plots of this type generally escalate. The situation gets worse and worse until near the end the antagonistic force is overcome. Along the way the protagonists and their companions might fall out (as frequently happens in the Harry Potter books), but in the end their goals unite them all together to help defeat the enemy. The world then is able to slowly return to normal for the vast majority of people.
The world through might not be the same for your protagonist. They might have had to make sacrifices along the way, had to overcome grief and they might have had to fight because they had lost everything in the first place. It might not be possible for the world to be the same ever again. They might not be heroes: they might have been acting because they were angry or frightened, or because their only other choice was to die.
What makes these types of stories interesting is the emotional trauma that the protagonist has to go through and overcome in order to get to the end. In Lord of the Rings there are many characters, but two of the most compelling are Frodo Baggins and Samwise Gamgee. No one will ever convince me that Sam was just Frodo’s companion (his gardener); he is very much his equal. He might not have been the first one who volunteered in Elrond’s Council to go to Mordor, but he stuck by Frodo’s side the entire way. The burden of the ring might not have affected him as badly as it did Frodo and Gollum, but he had the burden of watching his friend being destroyed.
For Frodo the world could never be the same again and he had to leave the world he helped to save in order to come to peace with what he had sacrificed in order to save it. For Sam the world got better; he found out that there was so much more to life than being afraid of love. That was how the same journey had effected those two characters.
In my opinion the journey characters go on to overcome threats can be some of the most compelling plotlines. The nature of threats to be overcome can be as complex and varied as the methods the protagonists try to overcome them. The thing to always remember though is the sacrifice of your characters in these stories, because it is their sacrifice that the reader will remember.