“What is instantiation of an idea?”
Ideas are manifested in the world through instantiation (also called incarnation). A particular object or event is an instance of a general type, and the type itself is an idea. In philosophical analysis, we can distinguish between ideas as mental entities that exist only when they are thought about and their instances which exist independently of anyone thinking about them. For example, consider that ‘table’ refers to a certain kind of thing—its essence (the idea)—but any specific table (an instance) has its own unique identity apart from other objects and properties.
Every entity and event in the world is an instance of some type or another, either physical or abstract. For example, a particular tree might be an instance of the ‘tree’ type. The idea of a tree exists independently in our minds (and possibly elsewhere), but the specific identity and existence of any actual, real-world object is independent of anyone’s perception or knowledge.
This is because a specific entity or event has properties beyond that which identify its type. A tree, for example, might have the property of being green—a quality not necessarily shared by other entities of the same type.
An idea can be instantiated in multiple ways. For example, a particular tree might have the same color as other trees, while a different tree might have the opposite color.
The most basic concepts are those which correspond to the lowest-level categories of being (object, property, quality). These concepts can be instantiated in many ways. For example, a particular object might have some specific combination of properties and qualities.
A more complex concept is that of life. It would be difficult to think of any specific instance or example, because the idea relies on a subjective interpretation (and definition) of what constitutes the property ‘life’, and this property’s relation to other properties.