Booking a room through Booking.com or Airbnb is something that I've done in the USA, France, Germany, Italy, Thailand, Czech Republic, and in the Republic of Korea. Doing so has always proved to be successful whether I stayed in a hostel, hotel, a house or someone's apartment. There are some unique things in South Korea that you should be aware of if it's your first time booking a room.
First and foremost, there's the map. Booking.com offers directions, and a quick click opens Apple Maps or Google Maps. Unfortunately, neither of these apps work very well in South Korea. Waze is the "go to" app for many foreigners because of its ease of use for English speakers. Naver is the app that the locals use, but it prefers the local language to English. My attempt to locate my last hotel led me for an hour-long quest filled with tears and frustration (not to mention a few choice words hurled at my phone!). Calling the hotel and requesting that they text you the address in "Hanguga" or Korean can be helpful enabling you to copy and paste it into the Naver app. You might also take a screenshot of your map destination and text it to the hotel for confirmation that you are on the right trail. I did just that and arrived at the hotel late after receiving their kind assistance. Koreans, in general, are incredibly friendly and helpful. The man at the check-in counter expressed his sympathy by giving me an upgrade to a suite at no extra charge!
Next, there's the room. Many a novice has entered the Korean hotel to find that the lights don't work! The trick is to use your room key. I mean, place it in the slot just inside the door. That will enable your power in the room. Removing it will also turn your electricity off, so I recommend that you leave it in. This ensures that occupants will "turn off" the lights when they leave their room.
Inside the room you will find slippers waiting for you. This is to encourage you to remove your shoes at the door. Often there is a robe that you can wear, and you should feel quite comfortable with your stay. Along with those amenities, you will find that many Korean hotels offer complimentary water and assorted beverages in the small refrigerator. This is generally the case in the less expensive hotels, and not the large luxurious ones that are more Westernized. Maxim coffee packets are very popular in Korea. Be sure to use the small cups for one packet. The large "coffee mugs" are best for tea and would water down the one coffee packet. Also inside the room is usually a computer, small towels (towels the size of "hand towels" in other countries are bath towels in Korea), a hair dryer, as well as large bottles of shampoo, conditioner, and body wash. Many hotels even offer a small kit with toothbrushes and toothpaste is almost always supplied in these small hotels. Some hotels even offer charging cords for Apple and Android phones.
Shower heads may be attached to your sink. Don't be alarmed, this is normal practice in Korea. There are drains in the floor so you needn't worry about containing the water behind a curtain. There are shower shoes provided so that you can keep your feet dry when reentering the shower room later. The bidet may be familiar to you, but the language may be a challenge. Just remember that all of the functions that you expect from a bidet (temperature, pressure, position adjustment, dryer, etc.) are available in Korea as well. Look at the pictures and don't be afraid to experiment with the buttons!
Other pleasant quirks of Korean hotels include provocative artwork, unexpected valet parking, perhaps a massage chair, a dryer, and large jacuzzi bath tubs! There are what many call "love motels." These motel rooms can be rented by the hour and often have very private parking areas. Some even have indoor parking and you can check-in with a credit card, never even seeing an attendant. You can usually spot these motels by the more secluded parking arrangements. These motels are as legit as the other accommodations and you will find the same amenities as the other low-cost sleeping solutions. Happy travels - Jaljayo (sleep well)!