As in many Asian countries, night markets are a staple of Taiwanese entertainment, shopping and eating. Night markets are open-air markets, usually on a street or alleyway, with vendors selling all sorts of wares on every side.
Many bargains can be had, and wherever prices are not displayed, haggling is expected. In the larger cities you will have a night market every night and in the same place. In smaller cities, they are only open certain nights of the week, and may move to different streets depending on the day of the week.
Every city has at least one night market; larger cities like Taipei may have a dozen or more. Night markets are crowded, so remember to watch out for your wallet! Shops selling the same items tend to congregate in the same part of the city. If you want to buy something, ask someone to take you to one shop and there will probably be shops selling similar things nearby.
Bargaining is OK and expected in night markets and small stores. Computer chain shops and department stores normally have fixed prices, but at least in department stores you may get a "registered member discount" if you're shopping a lot. Anyway it's always worth a try!
When bargaining at small stores, please note that the agreed prices are normally cash prices. If you like to use a credit card, the seller normally wants to add anything up to 5% to the price as a "card fee" etc. The fee consists actually of the credit company's commission and also the local sales tax/VAT. Even if you pay cash, you normally don't get an official receipt, as then the seller would have to report & pay their taxes in full (tax evasion is rampant). If you ask for a receipt or "fa piao", you will get it but you may need to pay 2-5% more.