I want to create a slide show- what should I download?
You need LibreOffice Impress for slide shows, but there is no separate download. There is just one single installation file for ALL of LibreOffice tools, Writer for writing documents, Calc for spreadsheets, Impress for slide shows, Base for database, Math for writing math formulas and Draw for drawing objects on images. You can download whole package from: https://www.libreoffice.org/download
If you only need (and you are sure you will not need any of the other office tools) then during installation just select LibreOffice Impress and uncheck all other products sub-components.