Ok, let's start with the Firewall. Your Firewall is your ability to stop opposing hackers, programs, and other threats in the Matrix from hacking you! Think of it like your Defense! Remember, when being attacked, you will be rolling your Firewall + Response to block the attack.
Speaking of Response, it's best to think of this as your Agility. Hack faster than your enemies? It uses Response (while in Full VR). Dodge a hack? That also needs Response. Many, MAAANY other situations where time is of the essence? You best believe that Response is your friend!
Your Signal rating is your effective range. The range table itself is pretty long, but so long as you're not using any bonuses or drugs to increase your Signal, the first 4 ratings are what matter.
Your Systems are, well, everything else. Keep in mind a few things. First, your Systems are limited by your Response: Low Response, Low Systems, even if your Systems are technically higher. Second, although it isn't your Matrix Health Condition, if your Systems shut down, you will automatically be booted from the Matrix. THIS WILL CAUSE DUMPSHOCK, AND IT WILL HURT.
...Oh right, Matrix Condition! For us, that is our real world condition! Remember that! If you get hurt in the Matrix, you will be injured in the physical world, and vice versa!
Now then, let's go back.