What's event region of @ in System Verilog?

In reply to dave_59:

I have question about this eg. In process 2, what region does the $display statement in? It’s blocked by the @ statement, should it be in some region after NBA? Or it’s still in the active region? When is it put into the event queue?

Similar question about the always@ block. Is it still in active region? What about the statement inside the always block?