Japan has numerous izakayas, which are casual places to eat and drink alcohol. Often, as soon as you are shown to your seats, before ordering anything, you may be served a small dish. This is called an otoshi*. It belongs to the izakaya culture, and can be considered a table charge that you will have to pay for at the end. Sometimes, however, there may be a separate "seating charge" in addition to the otoshi. In such a case, if you want to know what the charges are, you should ask the staff to explain before paying. Also, if you are a vegetarian or have types of food that you cannot eat for religious reasons, or if you are served something that you are allergic to, please communicate those things to the restaurant staff.
* Most izakaya restaurants take orders for drinks first, and only after the drinks have been brought to you will they take orders for food. During this time, guests will usually be hungry, so as a courtesy, rather than keeping people waiting for their food while hungry, the Japanese way is to bring a small dish of food for each person to your table that you can nibble on right away; that is the otoshi.