This area of the Unity User Manual provides a general overview of the principles of working with Assets in Unity.
An Asset is a representation of any item you can use in your Project. An Asset might come from a file created outside of Unity, such as a 3D Model, an audio file, or an image. There are also some Asset types that you can create in Unity, such as a ProBuilder MeshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
See in Glossary, an Animator ControllerControls animation through Animation Layers with Animation State Machines and Animation Blend Trees, controlled by Animation Parameters. The same Animator Controller can be referenced by multiple models with Animator components. More info
See in Glossary, an Audio Mixer, or a Render TextureA special type of Texture that is created and updated at runtime. To use them, first create a new Render Texture and designate one of your Cameras to render into it. Then you can use the Render Texture in a Material just like a regular Texture. More info
See in Glossary.