Slackware package series selection. You can select general categories of software to install in your system. Use up/down arrow keys to see all the choices. There is a description of each category at the bottom of the pane which could give you a basic idea of what the category is. For example, The A series, which is the base Linux system, contains the kernel and main system utilities. Use space bar to select or unselect category. Recommended software has been pre-selected, however you can safely un-select them if you think that those software are not necessary. If you are installing a server, you don't need those x-windows software, games, etc.