If half your catalogue is sold out, the product list at sale time becomes a minefield. This switch removes what you can't sell.
"Hide unavalible products and products without stock"
It saves on its own.
On the product picker — both in the order and in the POS — these stop showing:
And when you open a product with variants, sold-out variants disappear too: you only see the sizes and colours you still have.
Products without stock control. Since Jarbas doesn't know how many you have, it can't judge — they stay on the list.
Products that allow negative stock. You've already said they can be sold at zero, so the switch doesn't hide them.
The supplier purchase screen isn't affected either: there you still see everything, including what's at zero — which is exactly what you buy.
One important detail: with the switch on, a sold-out product disappears from search too on the sales screen. If you need to sell a specific item that's at zero, typing its name won't find it.
In that case: restock first, allow negative stock on that product, or turn the switch off.
Turn it on if you have a large catalogue with a lot sold out, or if someone other than you does the selling and mistakes are expensive.
Leave it off if you sell to order, or if your system stock isn't reliable — the switch will hide things you actually have.