One of the most important tools for query tuning is ability to view execution plans. They are even portable; you can send an execution plan to get advice from someone who doesn't have access to the underlying data. Have you even considered that sensitive information might travel along with the plans? Hugo Kornelis explains how execution plans affect data protection.
By looking at a query execution plan, you can determine which steps are used to resolve the query. But what if you just want to find out what the query plans are for only the queries that are currently running?
Erik Darling shows how execution plan estimates suffer.
Execution plans explain all you need to know about query performance, and how to fine-tune. Sure, you can see them in SSMS, but what if you need to drill into to the important details? What about using DMVs, Extended Events or SET statements to get at the execution plans? To get the best use of execution plans you need to be able to get right information from the right plan at the right time. Robert Sheldon explains how.
When something's wrong with your database you need to be able to identify the primary pain points within SQL Server and get to the root cause of the problem fast. Grant Fritchey explains how you can use execution plans inside SQL Monitor to help quickly and simply identify the problem.