There are certain assumptions one has to make with this site.
- The people asking questions are generally novices.
- The fact the question is being asked shows a lot about the knowledge levels of the user.
- You have to ask yourself what kind of capacitor it is most likely to be given the simple fact the question is being asked, and the way the question was asked.
Balance of probability: Wet electrolytic. It would be a freak occurrence if the OP was asking about anything else given the style of question.
Also, if you would care to click the link the OP provided - that looks very much like a drawing of an electrolytic to me - and the schematic clearly shows it's polarised.