Triggers in unity

 //for collision detection
 void OnCollisionEnter(Collision collision)
{   }
// for use of triggering 
void OnTriggerEnter(Collider other)
{}

//For 3D triggers remove the 2D (e.g. OnTriggerEnter(Collider collision)
/*There are three ways of detecting a Trigger:
-OnTriggerEnter(2D): Activated when player Enters the Collider 
-OnTriggerStay(2D): Activated when player Stays in the Collider
-OnTriggerExit(2D): Activated when player Exits the Collider */

public GameObject fire;

//This is for Specific Objects:
void OnTriggerEnter2D(Collider2D collision)
{
	if (collision.gameObject == fire/*Name of Object*/)
	{
    	//Your Code goes in here
		Destroy(Player);//this is an example
	}
}

//This is for Specific Tag:
void OnTriggerEnter2D(Collider2D other)
{
	if(other.tag == toHot/*Name of Tag*/)
    {
    	//Your Code goes in here
		Destroy(Player);//this is an example   
    }
}
//or
void OnTriggerEnter2D(Collider2D collision)
{
	if(collision.CompareTag("toHot")/*Name of Tag*/)
    {
    	//Your Code goes in here
		Destroy(Player);//this is an example   
    }
}

//This is for Specific Layers:
void OnTriggerEnter2D(Collider2D collision)
{
	if (collision.gameObject.layer == 3/*Layer Index/Number */)
	{
    	//Your Code goes in here
		Destroy(Player);//this is an example
	}
}