Elasticsearch difference between MUST and SHOULD bool query

Question

What is the difference between MUST and SHOULD bool query in ES?

If I ONLY want results that contain my terms should I the

Answer 1

As said in the documentation:

Must: The clause (query) must appear in matching documents.

Should: The clause (query) should appear in the matching document. In a boolean query with no must clauses, one or more should clauses must match a document. The minimum number of should clauses to match can be set using the minimum_should_match parameter.

In other words, results will have to be matched by all the queries present in the must clause ( or match at least one of the should clauses if there is no must clause.

Since you want your results to satisfy all the queries, you should use must.

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You can indeed use filters inside a boolean query.