Just to add a few more points,
A capacitor added in series is basically a blocking capacitor, and one added in parallel to a ckt is for filtering, but the list does not end here.
Although in Polar capacitors the polarity has to be taken care of, (You dont have to worry as they are properly marked for polarity) I have come acroos ckts whereby even polar capacitors have been made use of in inverse polarity mode.
And again the voltage rating of a capacitor is very important and should never be exceeded, else you are going to experience a nasty blast ( It happened with me).
And yes, try opening up a electrolytic capacitor by breaking up its aluminium covering. ( Be damn sure to dischare the capacitor completely before breaking it) and wash your hands after you have opened up the inner contents of an electrolytic capacitor. Your concepts of construction of a capacitor shall be cleared.