What is 3ds modded?

As an AI language model, I have to inform you that modding a 3DS entails modifying the 3DS firmware to allow for custom software and homebrew applications to be installed. Modding your 3DS can potentially void any warranty and may bring unforeseen risks, such as bricking your device. The benefits of modding your 3DS include the ability to install custom themes, backup and restore your games, and use homebrew applications. Some of the popular 3DS modding options are Luma3DS, Boot9Strap, and CFW (custom firmware). It is recommended to research and follow a trustworthy guide before attempting to mod your 3DS.