Its not a stupid question really. It has been asked but finding it would be just as much work as just answering it LOL
Actually there is a magic fart trail leading back to the offending anus. No one has the guts or true desire to follow it though.
Seriously think about it when someone farts in the room if you really wanted to know who did it and thought about it, you would know who did it. Asking out loud is just a uncomfortable response to it. Next time your in a room full of people and you smell one take a walk around the room and you will know who did it. Just dont make it obvious LOL
The olfactory senses are not much different then the other senses you have.
You see a light and you want to know where its coming from you follow the light trail to its source. Just because you yell out “hey where is that light coming from ?” dosent mean you cant figure it out.
You hear screaming and you want to know where its coming so you follow the sound to the source.
Works the same way with pheromones in a way except its not really the smell that triggers the reaction. It could smell like a fart and as long as the pheromone molecule was in there it would cause the same reaction.
Truthfully I dont think farts have pheromone molecules though LOL
Anywhoooo…
Pheromones are tiny molecules derived from your hormones that are secreted and carried off the body. Now they can come from various substances like urine, semen, vaginal fluid, saliva and sweat. Pheromones sold here are synthetic. No one is standing around collecting these fluids in a cup to sell to you. 
The heat of the body makes these pheromone molecules diffuse from the body and enter the air. Other people inhale those pheromones and they go up the nasal passage to the brain. In the brain they connect with various neurotransmitters firing a emotional response or a feeling like arousal, attraction, happiness… etc etc.
Its the feeling that causes the reaction not the actual scent. Now lets go back into that room of farters.
Your in a room with a bunch of smelly people and your diffusing some sexy pheromones. Your dressed neat, you combed your hair, did all the men grooming stuff men do.
The other guys in the room did all the same grooming. You however are leaving a sexy vapor trail that is causing a feeling. The ladies subconscious minds send up a hottie alert and they start looking about to find the source of this pleasant interesting feeling. They begin to follow that vapor trail because in there subconscious minds they know the prize is at the end of that trail. The closer they get the stronger the feeling until they follow that trail right to you.
Now once they follow that trail its your job to charm them. If you act like a dick they wont be interested no matter how arousing you may be.
Now you may be wondering well how do we know how to follow this feeling and why are they not aware of it.
Just like all other mammals… Humans are born with the ability to communicate certain things pheromonally. Its how babies bond with there parents. Its how they know your in the room when they cant see you. As we grow older and all the other senses develop we rely a lot less on the olfactory senses. They go on doing there thing but we tend to not really think about them till someone farts or grandma makes a apple pie.
If you really begin to pay attention to those senses you will begin to notice natural pheromones at work.
That instant connection you feel with a person you just met and cant explain.
The chemistry between two lovers who are totally wrong for each other in every other aspect.
Its why laughter is contagious.
Its why when one person is unreasonably afraid of something everyone else begins to feel uneasy about it.
I could go on and on…
These are all signals the body is sending that others in the room can pick up on and they cause emotions in us.
Now that that has been said… While pheromones are amazing and do cause all these neat feelings they are just part of the whole human package. So using synthetic pheromones just gives you a edge on the competition. They get you noticed. They wont do all the work for you though. Being able to control the signal your sending does make it a lot more easy and fun though. 
Tisha