CameraFollow.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CameraFollow : MonoBehaviour {

	public Transform target;
	public float smoothing = 5f;

	Vector3 offset;

	void Start()
	{
		offset = transform.position - target.position;
	}

	void FixedUpdate()
	{
		Vector3 targetCamPos = target.position + offset; //transform.position is current position, targetCamPos is 
		//the position you want to be at 
		transform.position = Vector3.Lerp (transform.position, targetCamPos, smoothing * Time.deltaTime);
	}
}