BUI (Buffer User Interface) is a library for making 'list' (similar to "M-x list-packages") and 'info' (similar to customization buffers) interfaces to display various data (packages, buffers, functions, etc.). It is not an end-user package, it is a library that is intended to be used by other packages. Basically, at first you define 'list'/'info' interface using `bui-define-interface' macro, and then you can make user commands that will display entries using `bui-get-display-entries' and similar functions. See README at for more details.