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The only dumb question is the one that doesn't get answered.
I'm a cli kind of guy...
df - report filesystem disk space usage
Open a shell with that icon that looks like a monitor with a shell overlaid and issue
$ df -h
and get something that looks like
bash-2.05b$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hdc6 957M 693M 265M 73% /
/dev/hdc1 79M 34M 45M 44% /boot
/dev/hdc2 49G 3.7G 45G 8% /home
/dev/hdc3 4.7G 2.0G 2.8G 41% /usr
/dev/hdc5 1.9G 60M 1.9G 4% /var
/dev/hdc7 1.4G 33M 1.3G 3% /tmp
/dev/hda7 14G 8.7M 14G 1% /DATA_FAT32
/dev/hda8 4.7G 4.0K 4.7G 1% /TEMP_FAT32