Reza Rad gives people a primer on Apache Spark:
Microsoft Fabric runs some workloads under the Spark engine, but what is it really? In this article, I’ll take you through the question of what Spark is, What benefits it has, how it is associated with Fabric, what configurations you have, and other things you need to know about it.
Reza talks a bit about history, interaction with languages, etc. As a quick addition to the languages list, you can use .NET languages like F# and C# with Spark, though it does involve setting up dotnet/spark and there are some open questions about its future. And I’m not even sure you could get it to work with Microsoft Fabric.