By bringing the Bishop here
		
		
	 
	
		
			White prevents Black from undermining the centre
		
		
	 
	
		
			Due to this pin
		
		
	 
	
		
			So black moves this pawn forward
		
		
	 
	
		
			White responds by advancing this pawn
		
		
	 
	
		
			And after this move
		
		
	 
	
		
			He simply develops the Queen
		
		
	 
	
		
			Takes this pawn
		
		
	 
	
		
			And gains a solid pawn chain
		
		
	 
	
		
			While Black has this weakness