Spanish has a curious little symbol, the ‘diéresis’, which is these two dots that you’ll occasionally find over the letter -ü-. You won’t find them with any other letter because they serve a very specific purpose: to unmute the -u- in a context where it usually wouldn’t be pronounced, that is, after -e- or -i-. Words like ‘guitarra’ are pronounced with a hard -g- followed by an -i-, but words like ‘pingüino’ (penguin), ‘lingüística’ (linguistics) and ‘vergüenza’ (shame) do require you to pronounce the -u- sound.