Unlike NASCAR where you are given a set template which your car must conform to, f1 engineers can design the car how they see fit, as long as it is within the rules. Each car is very different.
The Lotus that Alonso was looking at is very good this year, probably better than Alonso's Ferrari in many ways. And teams are very protective of their designs and you very rarely get to see your opposition cars up close like that. He would be just taking mental notes of anything he thought may have looked interesting so as to tell his design engineers later on during debriefing.
Teams also hire professional photographers on race weekends to take high detail shots of opponents cars so he is unlikely to notice anything that the engineers havent already spotted, but that won't stop him from checking it out just to see for himself.