should I restore backup? illegal block inode

[Tim M]

A few minutes ago I tried to walk my laptop up from hibernation and
there must have been a corrupted file because fdisk (or something like
it) started. Then I got a list of problems. such as:
Illegal block #12 (169995442 mode 1721952, cleared.
clear inode
[many lines of stuff]
too many illegal blocks in inode 1721953 clear inode <y> ?
I answered yes each time it said clear inode (having no idea what an
inode is but the default answer was yes so I went with that.
Then I got a line (1704591 is (then null mode 0 [here I cannot read my
own writing]. should be /usr/share/gnome/help/gnome_netstatus/ (ko
C1704550). [something like that . . . again my writing leave a lot to
be desired]
Symlink . . . inode #1704594 is invalid clear <y>
I answered yes  to each question when it had finished complaining to
me I tried to use the command; startx but got an error screen
however I issued the command reboot now and it rebooted normally and
connected to the router.

My question is what is inode and what are illegal blocks? Does this
mean that my system might have been hacked? Should I reinstall from my
last backup?

Thanks in advance, Tim