iTunes Match music storage and playing songs

I have iTunes match and about 75% of my songs are in the cloud and I cannot play them on my computer if I'm not connected to the internet (obviously) so why do they still take up space on my computer? I have about 42GB of music on my storage when I definitely have less than 1000 songs actually downloaded in my iTunes. Also, the songs that I don't have downloaded will not play and are grayed out even when my iTunes match is turned on and I'm connected to wifi.