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So what is the aggregation framework? The aggregation framework in its core is just an alternative to

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the find method you could say. You have your collection and now the aggregation framework is all about

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building a pipeline of steps that runs on the data that is retrieved from your collection and then gives

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you the output in the form you needed

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and these steps are sometimes related to what you know from find, match

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for example here is the equivalent to filtering in the find method, it allows to filter down your results

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and you get a lot of different steps you can combine as you want.

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You can reuse certain stages,

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for example you could match again later too to filter your already transformed data a bit more and therefore

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you have a very powerful way of modeling your data transformation.

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Every stage here in this pipeline receives the output of the previous stage and therefore, you can have

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a very structured way of having some input data and then slowly modifying it in the way you need it

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in the end.

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Now in this module, we'll have a look at a lot of stages of the aggregation pipeline and that is just

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what this aggregation framework gives you, this pipeline you will build. Now we'll build this pipeline

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together, no worries I'll show you in detail how it works

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and as you can see in the official docs, there are loads of different stages you can have,

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so these are basically all stages you can combine in the pipeline.

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Now I'll dive into a lot of them in this module but it's impossible to cover all of them,

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so I strongly encourage you to also go ahead and dive into these docs on your own and play around with

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these steps, take some dummy data and simply see how you can transform it,

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this is the best way of then learning more about the aggregation framework.

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But of course, let's now first get started and let's understand how exactly the aggregation pipeline

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works.