So i just purchased a Blackwidow ultimate stealth and it said to download that in the manual... What is it exactly? and when i go to the link i cannot find my exact keyboard.
Synapse is the utility software used for most of Razer's hardware. It's used mainly for configuring various customization options, like macros and such.
It's the program you can use to save settings for your keyboard/mouse and sync it across different computers, as well as set up macro keys (which is why you bought the keyboard in the first place, I assume).
It's awful software that people seemingly just complain about. You should still be able to keybind the extra keys in most games, even without installing the software. The only thing you'll miss out on is being able to set up automated macros. Said automated macros will get you in trouble in nearly every multi-player game anyway.