As I couldn't think of a new topic, a friend suggested a post about plots. Face it, plots are my weak point - at least coming up with a main plot. But I know the importance of having an actual main plot.
But what is a main plot? In abstract terms it's the skeleton that keeps up your story. On that plot you can hang the flesh (characters), the muscles (the action), the subplots (the brain) and the descriptions (clothes).
I just made those metaphors up. Or are those similes? Never mind. The main plot! In a specific example of what can be seen as the main plot, let's look at a few examples from literature and films.
Lord of the rings - the quest to defeat Evil
Streetdance - to compete and win the british streetdance competition
Transformers - find the Cube
Sahara - find the ironclad ship/the plague source
Pretty Woman - prostitute getting off the streets
Runaway Bride - Writing a piece about a woman who deserts men at the altar
Why is it even important to have a main plot? Because it's the red thread that ties everything else together. You need a focus when writing, something that the readers can hold on to when you swivel out into the bush (those are the fun moments, right?). Personally, these main plots usually come AFTER I got the story. My story is the characters, the subplots. It's not like this for everyone. Some might even get a "duh" reaction to this post because the main plot is their starting point and therefore natural.
But the main plot doesn't need to be what the story is about. My main plots include "the universe rule is threatened by rebels" (the story is about love beyond the norms), finding a lost familiar (it's about love and guilt and facing hardships instead of running from them) and a detective looking for a missing person (about the good in people despite the darkness around them).
I might be rambling, and I feel I'm not very clear on why you need it, but that doesn't keep me from being certain an overarching structure such as this is vital for any story. Without it, you can't have a beginning and an end. You can keep adding small plots and events forever - it's like a real life!
A writing teacher once taught me how to write a short story by the suggestion to look at it as a small piece of a cake. Novels are the same - just includes a larger piece. No matter how much I'd like to, I've never been able to gobble down a whole cake. If I did, I'd probably be sick of it. But getting a small glance out of a life, that's delicious.