This list of objects in the Chronicles: Battle for Greece DLC doesn't include any Gaia objects because they are almost exactly the same as in AoE2 DE. The only difference is the new Mouflon huntable animal unit (ID 2340).
For more info on what dead units, projectiles, lines, sets, and classes are, click here.
For a list of objects in AoE2, see the AoE2 Objects Table. For a list of objects in the Chronicles: Battle for Greece DLC, see the Chronicles: Battle for Greece Objects Table.
The Dead Object ID belongs to the decaying object that is placed on the map when a unit is killed or a building is destroyed. AIs can count the dead objects they own, but they can only be counted by individual IDs. cc-players-unit-type-count is required to count the dead objects of other players.
The Proj. ID belongs to the projectile object that is created when a ranged object fires a projectile. These IDs are not the same as ProjectileType. cc-players-unit-type-count is required to count the projectiles of other players by ID, so using up-projectile-detected is recommended. If two projectile IDs are listed, the second ID is used in addition to the first projectile ID when the object is firing multiple projectiles.
Lines group together a base unit and its upgraded versions so that you can easily count a unit type without having to know which upgrades have been researched. Sets combine multiple related units or unit lines together so that they can be counted more easily. Classes group together similar types of units, such as infantry or warships.
For a list of Class ID values, see ClassId. For a list of Line ID values, see LineId. For a list of Line ID values, see SetId.