This is a sub par system unless you are paying 300$ or less for the entire setup.
Magnetic shielding means you can place the speaker near a tv monitor and it will not distort the image.
Two way means you have two seperate drive components in one speaker assembly. IE in your case a high range tweeter and a mid range woofer. In some cases you might have a 3 way speaker, like a large floorstanding speaker, and this would have a tweeter, mid range driver, and a low range woofer.
In most applications a 6.5 inch sub will not do the job. Problems arise like, frequ response ( total range your setup can reproduce), DB ( how loud it is), and distortion.
Impedance: 4 Ω means that the ohmic resistance is 4.