Maslow's Hierarchy of Needs is a way of showing how humans prioritise different needs in their lives. The psychologist Abraham Maslow identifed this hierarchy in 1943, and it gives a very good indication of the relevant importance of different needs.
The theory is that the needs at the bottom of the pyramid are the most compelling. If they're not met, our whole focus is on getting those needs met, and none of the higher needs are even considered.
Then, as soon as those needs are met, we start looking to meet the next ones on the list; and as soon as they're met we start on the ones next up the pyramid and so on.
For writers, Maslow's Hierarchy of Needs is important because it allows us to identify what our characters might want. As I explain in How many plots are there anyway?, there's really only one story: a character wants something and can't have it.
The thing the character wants can be sourced from Maslow's Hierarchy of Needs.
Have a look at the diagram below, reading it from the bottom up:
As you'll see from the diagram, the needs at the bottom of the pyramid are our survival needs: food, water and shelter. They are the primary needs, and if we don't have those, nothing else matters.
The next category on the pyramid are our safety needs. (This means that we'll compromise our safety in order to get food. And that makes sense - fishermen going out on rough seas, for example, or cave-men hunting big mammoths even at their own risk.)
The need for food, water, shelter and safety are very primeval needs. Our very survival depends on meeting those needs. So they're rich with possibility for the writer.
Many stories are based around getting those basic needs met. Every disaster movie ever is about escaping from the disaster: i.e. getting the safety needs met.
If you have your story based around your characters needing one (or more) of those things then they'll resonate deeply with the reader. You won't have to explain why this need is so important to your character - it'll be self-evident.
The next need is the need to love and belong. Again this is a very deep and primeval need. Of course all love stories and romances fall into this category.
The next needs categories are:
the need for self-esteem, and esteem by others,
the need to realise our potential, and
the need for self-actualisation (which is also described as our need for spirituality).
These top three needs aren't quite so primal, and they'd be more difficult to base stories around. Stories based around these needs would be more highbrow perhaps, more literary rather than commercial. They would be very character-driven stories rather than plot-driven stories.
I personally think that stories based around the top three needs would require more writing skill - we'd have to really do a good job showing the readers why the character needed to sort out her spiritual crisis (or whatever). We'd have to write really well in order for the reader to care!
I'm not saying that it can't be done; I'm just saying that it isn't as easy.
You can use Maslow's Hierarchy of Needs to make sure your plotting is consistent. Make sure that your characters are getting their lower-level needs met first. In other words, they're never going to engage in a romantic encounter if they're hungry or in danger.
Also, if you're stuck in your story and wondering how to progress it, you could make something happen which threatens those lower-level needs.