When using Gentoo sometimes you face the situation that you just need to add something to your keywords file. More specifically portage will tell you something like: the following keyword changes are required in order to install packages x and y…
Keywords are basically words, whill tell your Gentoo box what is suitable or desired to be installed in your box. Keywords can also be used to install packages, which are not so stable in general use – so caution is adviced before actually enabling any extra keywords.