Age of Empires 4 classifies all objects you can place in maps as either an Entity, Squad, or Visual.
These classifications determine where these different types of objects are stored and how they are used.
Every interactive environment object in the game is referred to as an Entity, such as buildings, trees, berry bushes, stone deposits, gold deposits, and walls.
An Entity's Blueprint defines what kind of object it is.
Entity Blueprints are defined in the Attribute Editor (see Tuning Packs documentation), and contain all of the details and statistics for that object, including the model the entity uses, it's health value, collision volume, and other relevant key attributes.
Entities can be found under "EPBS" in the Object Browser, and dragged into your custom map.
Examples of entities can be seen below in buildings, trees, and bushes, as they all either possess health, block unit movement, or can be interacted with.
Entities labelled as "CORE" in the object browser are only data templates for entities and should not be used, as they do not have visuals attached. To import specific buildings and units, navigate to the specific area for a civilization's units or buildings and drag them onto the map from there.
All units and creatures are referred to as Squads.
A Squad can be composed of multiple entities such as a group of spearmen or deer, or a single entity such as an individual spearman or an individual deer. Both multiple and single units are treated as "Squads" to simplify how these units operate in-game when they respond to damage, commands, movement, and similar effects.
Similar to Entities, Squads have blueprints which define what type of squad it is.
In the Object Browser these blueprints are referred to as "Squad Blueprints," or "SBPS," and can be imported by dragging them onto your map.
Similar to Entity Blueprints, Squad Blueprints are also defined in the Attribute Editor (see Tuning Packs documentation). The details in the squad blueprint define what kind of entities, and how many, make up that squad.
The examples below show various things the Age of Empires 4 considers "Squads."
Everything is Squads
Within Age of Empires 4, technically all "Squads" in the game consist of individual units. When several units are grouped together in a formation, they are a "Group" of "Squads," since each can be individually controlled, but can receive orders together.
Visual Objects, or "Vis Objects" have no functionality, cannot block units, have no health, and cannot be destroyed.
This makes Vis Objects inexpensive to implement from a performance standpoint, and are a readily-available, low-cost way to add visual interest to a map.
Any piece of art normally used as an interactive Entity or Squad can also be placed as a simple Vis Object, which removes any normal functionality or interactivity they have, converting them to a static piece of art on the map.
Vis Objects can be either static or animated, with some possessing various forms of animation, such as bushes that blow in the wind, or campfires that emit fire and smoke
Visual objects can be found in the Object Browser under Art, and dragged onto your custom map.
An example of a Vis Object could be a small camp constructed of various vis objects.
In the example shown below, an army of units would pass right through this little camp and it cannot be destroyed by siege weapon fire and other destructive effects.