Ext2 is the Extended Filesystem (version 2). Ext2 grew out of the MinixFS, which had some very strict limitations.

Ext2 was the filesystem which everyone used for Linux for many many years, however, it's new successor Ext3 has started to become popular.

Ext2 in particular has no journalling support, and is bad at handling directories with huge numbers of entries. (Over 1,000 or so).

Ext2 has an excellent fsck which can recover from most situations, since Ext3 is very similar to Ext2 it also uses fsck, even though it doesn't necessarily need to, since it has a journal.

-- not true! The journal helps recover from a crash, as you know where you were writing to when the power failed, so you can check only the affected files. However, ext3 partitions still get checked irregularly (eg mount counts, time limits) to ensure that the file-system is consistent. Hard drive errors can still introduce problems. -- JohnMcPherson