True instancing is when multiple copies of the same object share one set of geometry and material data in memory, allowing the system to draw them all with a single instruction.

This drastically reduces CPU and GPU overhead compared to spawning full individual copies, making it ideal for rendering many identical objects like trees, crates, or bullets.

....this essentially lets you use anything as much as you want for free GPU rendering and performance heavy detailed items.

Not to be confused with Material instancing, which is the same exact process where the only new relevance is the values changing such is if you hue shift something blue or red using the GPU (from a white/grey texture with a white/black layer map)

So for example in second life this could function like so:

1 object in a build lets say a detailed column. it can then be set as the Instance Root and have Instance Child objects all connected to 1 thing, no matter which of them you make edits too it all happens to the root object and all child Instances part of this specialized new link-set are changed to match. 1 column lets say 4 land impact and you can rez as many columns as you like and it only counts towards the 1 column that its 4 land impact.