how can point at plan with mouse ?

Hi all
i couldn’t work with raycast apropritely !
i wanna point at a special x & y on plan and actually do it by mouse .
i mean the raycast moved every where mouse goes . i can’t handle it . . .

make a scene with something with collider on it

attach script with this to any object:

void Update()
	if (Input.GetMouseButtonDown(0))
		RaycastHit hit;
		if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit))

play the game, press left mouse button while cursor over the collider abd note you got world coords of hit in console.