Linux supports many different filesystems, but the most common one used is probably the ext2/ext3 filesystem. The ext3 filesystem is just a journaled version of ext2. This filesystem supports the standard UNIX rwx for user, group and others permission scheme. An explanation of this is located here. Some of the other filesystems supported by Linux are fat(12,16,32), ntfs(limited), ReiserFS, XFS, JFS and a ton of others. A look through the kernel source tree will reveal all of them.