I'm a beginner ,I can't understand "Component" well . can anybody give a answer which understand easily
A component is essentially a script you can add to your gameobject
You could add, e.g a MeshCollider, via scripting like this with C#
gameObject.AddComponent<MeshCollider>();
Component is a base class for all components - scripts, renderers, colliders, etc
For a script, the structure of inheritance looks something like this:
System.Object > UnityEngine.Object > Component > Behaviour > MonoBehaviour > YourScript
It's anything you can see in the Inspector, with a twirly triangle on the left. Most of these can be dragged onto a Game Object, and the others can be added from the "Component" menu.
A GameObject is made up of parts that you add to it.
As a real life example, look at your house you live in. Your house is made up of all kinds of parts, or components. What kind of components? All houses have a door component, many window components, a heater component, many light components, sink components, etc.
In Unity, components are the parts that you attach to your GameObject. The parts, or components, that you attach, or add, to your GameObject are what makes your GameObject do the things you want it to do.
When you make a new GameObject in Unity, it can't really do much at all because it doesn't have any components, except for one. All GameObjects, even newly added ones, have one part, or component, called a Transform.
The Transform component allows the GameObject to move around in your game.
Is that basic enough, or do you need more info?