What is tempdb, and why is its configuration particularly important for overall SQL Server performance?

Tempdb is a special system database used by SQL Server for temporary objects like temporary tables, sorting operations, and row versioning, and since it is shared across the entire instance and heavily used by many different operations simultaneously, properly configuring it, such as using multiple equally sized data files, can significantly reduce contention and improve performance across your entire server.

-- Adding multiple tempdb files to reduce contention
ALTER DATABASE tempdb ADD FILE (
  NAME = tempdev2,
  FILENAME = 'C:\Data\tempdb2.mdf',
  SIZE = 512MB
);