Character passing through colliders

The movement of our character in our game is controlled by the below mentioned script, but while moving the character passes through game objects with colliders n rigid body on them. Can you suggest how I can stop my character to pass through the game objects with colliders and rigid body on them.

void Update ()
{

this.transform.position = this.transform.position +this.transform.forward * speed;
this.transform.Rotate (Vector3.down, turnDisplacement);

}

As mentioned in above comments, you don’t use transform.position to move things that are expected to work with Physics and colliders.