Clustering is a Windows OS feature, SQL Server is only cluster-ware application.
A node is a machine part of the cluster; a cluster can have 2-n nodes. Common are 2 nodes; an active and a passive node.
SQL Server instances has nothing (directly) to do with clustering. On one machine you can install up to 50 named, independent SQL Server instances, see
Database Engine Instances (SQL Server)
BTW, SQL Server related forums moved to Question & Answer at https://docs.microsoft.com/en-us/answers/products/sql-server
Olaf Helper
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