Awesome. 

Firstly, if it stains yellow, discard it. This is a toxic (inedible) Agaricus xanthodermus. 
Secondly, if it smells like phenol, discard it. This is a toxic (inedible) Agaricus moelleri. 

If no yellow stain nor smell of phenol are present, then it might be one of these five edible specimens:

- Agaricus arvensis
- Agaricus bitorquis
- Agaricus bisporus
- Agaricus bernardii
- Agaricus campestris

Let's be 100% certain before consumption! 

Discretion is highly advised.