Borderless mode is a game mode in Google Snake Game which removes the outer border entirely, seemingly extending the board.
However, the board is still the same size as in the standard game mode, as it loops around. While the board itself seemingly has no center, the snake always stays in the center of the screen, meaning the camera always follows it. Once the snake is long enough, you will be able to see other parts of the snake around the board, meaning the border acts in essentially the same way as it does in Peaceful Mode. The snake still dies from colliding with itself.
The game mode otherwise acts the same way as Classic Mode.
The name of Infinity/Borderless mode was decided on after a long argument in the Google Snake discord server. The mode was originally named walless referring to the fact that there are no walls that can be hit on the mode. Runner Ploverums said "lets think of a better name than walless" bringing up the name infinite. Runner LilJapKid was in agreement to change the mode's name, but disliked the infinite name, saying "infinity mode sounds misleading though." A few more names were thrown around such as Borderless, and with most people wanting one or the other, the name was compromised on and became Infinity/Borderless.
Later on it was decided to stick with only Borderless mode, to make things simpler for everyone.
I edited this to correct the grammar