I am nowhere near as eloquent as you are, but I can try clarifying what I mean by giving an example.

• Dropping a drop of chemical into a beaker...
• Growing cells in a Petri dish...
• Placing a boy rabbit and a girl rabbit in the same cage...
• Smashing a vase with a hammer...
• Shooting an accelerated helium nucleus against a gold plate...

...and seeing what happens, are all "real world" experiments. Some of them are more constrained than others but they are all real objects in our own world.

In contrast,

• Feeding a computer program with a set of formulas describing what happens when you do any of the above and running that program...
• Shifting toy battleships over a map...
• Following a board game, with or without an actual board...
• Writing a story in a book...

...are all simulations. The objects in these scenarios are not real objects in our reality, only their representations. But in their own reality, they are very real. What for you are two toy battleships moved around the map, from the point of view of those battleships may be a real naval combat with real people screaming in agony. Characters in that book are just words on paper in our world, but in their own they are real people with real problems, dreams and ambitions.

The word "simulation" does not necessarily have to involve a computer. And I do not necessarily restrict my definition of a "computer" either. A "computer" in my view is "any autonomous device that can execute the simulation without an external interference". Three out of my four examples do not involve any such device.