It is just that a polarized capacitor must not be connected with the + terminal negative with respect to the - terminal.
They are often used where there is a DC voltage present and this must be connected the right way around.
They can explode in a very spectacular and messy way if you do it the wrong way.
Thank you for the response, it has been very helpful. But if a voltage is applied to the capacitor, will the current flow directly through the capacitor, or will the voltage have to charge the dielectric before the current can pass through.
The DC current only goes into the capacitor to charge it. When you discharge the capacitor, it comes back out again.
It does not really "pass through" the capacitor.
This applies to any capacitor.
The charge on the capacitor eventually gives the capacitor a voltage on it equal to the applied voltage and at that time no more charging current flows into the capacitor. You can take the capacitor and put it away and the charge will still be there.
When you connect it to a conductor between the plates of the capacitor, current will flow out of the capacitor into the conductor. If you leave it there long enough, there will be no more current flowing and the capacitor voltage will drop to zero.
Electrolytic capacitors behave exactly like other capacitors except that if there is a dc voltage present it should be the right way around.
What might not be obvious is that AC voltages and currents can pass through capacitors while DC voltages and currents cannot pass through them.