Your description is quite confusing, but no worries.
A “class” is a term used in programming, and pretty much everything in Unreal is a class. Classes can be created both in C++ and Blueprint.
An “Actor” is a class called “AActor” (the first “A” is silent and refers to its type as “Actor”). The top-most level in Unreal is a “UObject” (“U” standing for Unreal Object), and AActor inherits from that as a child class. Any class with the prefix “A” (so “APlayerController” for example) is an object, Actor, that can be placed in the world. Any class with the prefix “U” is a standard object that cannot be placed in the world.
A “component” is a part of an Actor. A SceneComponent has its own transform within an Actor, while an ActorComponent only adds behavior.
In your screenshots, the PointLight is an Actor that contains the PointLightComponent that is the actual point light. The Floor object is a Static Mesh Actor that contains a StaticMeshComponent that holds the actual 3D mesh, materials and other properties. In these cases, the Actors just “wrap around” the Components so you can place them in the level. If you create your own Actor class, you can add any number of components. So for example a light fixture would have a StaticMeshComponent that has the 3D mesh and material for the visible fixture, and a PointLightComponent so it emits light. This way, you only have to place that one Actor in the world to have a working lamp, as opposed to manually placing each Static Mesh Actor and Point Light Actor.