Smile = both corners of your mouth point upwards, sometimes the teeth are seen as well. Most people smile when their picture is taken.
Laugh = when people actually produce a 哈哈 sound, usually after someone tells a good joke or when you watch a comedy or something
Of course, there's also a different kind of laughing. This is called 'laughing at someone'. For example, someone does something stupid and people laugh at him for being such an idiot.