What a Thread Is, What It Costs, and What Stops It

Five things this topic established, and where each one was.

What the topic established, and which card it was on
The thing	Where
`start()` creates a thread; `run()` is an ordinary method call	Why Calling run() Directly Started Nothing
Each thread's own order holds; the interleaving between threads does not	Two Threads Printing at Once
A thread runs once and cannot be restarted	The States a Thread Moves Through
A virtual thread is scheduled by the virtual machine and costs almost nothing	A Platform Thread Against a Virtual Thread
The process exits when the last non-daemon thread finishes	Why Your Program Will Not Exit

A thread buys overlap and spends ordering. Everything in the topics after this one is about the consequences of that trade, and none of it is visible in code that runs on one thread.

Java
Concurrency