The Linux kernel supports many different kinds of filesystems:
The third extended filesystem. A journaling filesystem, this has been the default for most Linux distributions since the early 2000s.
The second extended filesystem. This was the initial default Linux filesystem. ext3 is basically ext2 with journaling support.
Journaling filesystem created by Silicon Graphics for IRIX and ported to Linux.
This was the first journaling filesystem introduced in the standard Linux kernel.
A Microsoft Windows filesystem for Windows 95, 98, and ME systems.