The Room List is a feature within all versions the Flash-based Bonk.io, as well as the HTML5-based Bonk.io and its development. It is used for players to join or to create a Custom Game. It is a list of every Custom Game room that is currently online when it is loaded, ordered from the players closest to one's IP location to farthest away.
How To Use (HTML5-based Bonk.io)
Within the HTML5-based Bonk.io, every room listed goes back and forth between a white and light grey background, with black text, unless a friend of a one is within a room. In which case, it will appear in blue text.
Aside from this, every room listing follows the same format, being:
Game Name - A option for players within the game to create their own custom name, it is by default the user's Account/Guest Name.
Player Amount - The count of the players within the room, if it is full, then no more can join, until one within the room leaves. A room can only have up to 8 players.
Mode - The mode that is currently being played within the room.
Password- A lock symbol that shows if a room will require a password in order to enter it.
Min/Max Levels- The levels of players that are allowed to join a certain room.
Distance - The miles away a player's IP is from yours.
Flag Symbol - A symbol of the player's IP location country flag.
Overhead, players can choose to hide/allow rooms that are passworded. Below, there is the create button which takes a player to the Create Game feature. There is also the Join button which allows for a player to enter a room after selecting it and a refresh button to refresh the room listings. Lastly, there is a Mode Filter option, which allows for players to choose which rooms by gamemode become shown in the room list.
Create Game
Upon clicking the Create button, players have a menu to fill out in order to create a Custom Game, the following options include:

This is an example of a player filling out the Create Game feature in the HTML5-based Bonk.io. This is taken before the October 16, 2020 update. Aside from color differences, there are no physical changes since then.
Game Name, Password, and Player Amounts, Min/Max Levels have all been mentioned above, and are features within this.
Aside from this, there is an unlisted button which allows for the map to be hidden from the Room List. Lastly, there is the option either to cancel or to create the room.
Differences From the Flash-based Bonk.io
*Note that all information below is based on the latest update of HTML5-based Bonk.io compared to the final update of the Flash-based Bonk.io affecting the features and can be subject to change.
Missing Features- Mode Mentioning, Mode Filters, Min/Max Levels, Unlisted Rooms* (with multiple people), an overhead listing of the Room List columns.
Exclusive Features-
- A mentioning of the Game Progress in the Room List (In Game/Lobby)
- Being able to custom search for a room with any mode you would like with the filter bar at the bottom right
- Being able to create a room with "0 players", causing an unlisted room to be created, though it was only able to be a fully private room, meaning that no other users could join it.