My 3rd Person camera doesnt collide with Terrain... Please Help

Hi mates, im on Unity 5 and i am making a 3rd person game. I have a Player and a camera that has a CameraOrbit script to follow and turn around the player. This is the CameraOrbit script:

 using UnityEngine;
 using System.Collections;
 
 public class CameraOrbit : MonoBehaviour
 {
     public Transform target;
     public float distance = 10.0f;
     public float xSpeed = 5f;
     public float ySpeed = 2.5f;
     public float distSpeed = 10.0f;
     public float yMinLimit = -20.0f;
     public float yMaxLimit = 80.0f;
     public float distMinLimit = 5.0f;
     public float distMaxLimit = 50.0f;
     public float orbitDamping = 4.0f;
     public float distDamping = 4.0f;
     private float x = 0.0f;
     private float y = 0.0f;
     private float dist;
 
     void Start()
     {
         dist = distance;
 
         Vector3 angles = transform.eulerAngles;
         x = angles.y;
         y = angles.x;
 
         // Make the rigid body not change rotation
 
         if (GetComponent<Rigidbody>())
             GetComponent<Rigidbody>().freezeRotation = true;
     }
 
     void LateUpdate()
     {
         if (!target)
             return;
 
         Vector3 oPos = transform.position;
 
         x += Input.GetAxis("Mouse X") * xSpeed;
         y -= Input.GetAxis("Mouse Y") * ySpeed;
         distance -= Input.GetAxis("Mouse ScrollWheel") * distSpeed;
 
         y = ClampAngle(y, yMinLimit, yMaxLimit);
         distance = Mathf.Clamp(distance, distMinLimit, distMaxLimit);
 
         dist = Mathf.Lerp(dist, distance, distDamping * Time.deltaTime);
         transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(y, x, 0), Time.deltaTime * orbitDamping);
 
         transform.position = transform.rotation * new Vector3(0.0f, 0.0f, -dist) + target.position;
     }
 
     float ClampAngle(float a, float min, float max)
     {
         while (max < min)
             max += 360.0f;
         while (a > max)
             a -= 360.0f;
         while (a < min)
             a += 360.0f;
 
         if (a > max)
         {
             if (a - (max + min) * 0.5f < 180.0f)
                 return max;
             else
                 return min;
         }
         else
             return a;
     }
 }

It works well, but the problem is that my camera pass through the Terrain, it doesnt collide with it... I have checked a lot of scripts but i dont find the solution. Can anyone help me? But please be so specific because i am noob on Unity. I dont have any collider or anything on the camera because i dont think it is the problem... Thank you so much mates :)