I is best always to get 4 wire usb cables.
The 2 wire is power only, i.e. no data and will not support any fast charge schemes with phones or tablets, some may even refuse to charge with a 2-wire cable.

Other usb powered equipment will often work fine with 2 wire cables, because they ignore any fast charge schemes and just draw the power they need.

To test if a cable is 2 or 4 wire, use it to connect a phone/tablet to a computer, if the computer sees some new equipment it is a 4 wire cable (It do not matter if it recognises it).