You can use /co for a list of commands, and /co help <command> for extra information about a certain command.

In this tutorial I am only going to cover /co inspect, and /co rollback</command>

/co inspect toggles the block inspector mode on, or off.

You can left click on any block to see which blocks were there previously, how long ago the action happened, and who placed them.
You can right click on containers to see what items have been added, and removed from the container, who by, and how long ago the action happened.

You can also use /co l <page> if there is multiple pages.</page>

You can roll back the last 10 minutes, day, week, or even make it as if the player never joined at all with /co rollback.

This is a really powerful tool, and can cause a lot of harm to your server if used incorrectly.

Here is how to use it.

Replace <username> with the name of the player you want to roll back. (The name of the griefer!)
Replace <time> with the amount of time in whatever unit you choose.
Replace <time unit=""> with the unit you choose.

m = minutes
h = hours
d = days

/co rollback u:<username> t:<time><time unit="">

For example, if I wanted to roll back everything I have done in the past 15 minutes I would run the command

/co rollback u:AmazinglyJava t:15m

If I wanted to roll back everything I have done in the past 1000 days I would run the command

/co rollback u:AmazinglyJava t:1000d</time></time></username></time></time></username>

• Log blocks broken by players
• Log blocks placed by players
• Log natural block breakage (ex: if a sign pops off a dirt block that was broken)
• Log bucket usage
• Log liquid flow
• Log tree growth
• Log mushroom growth
• Log vine growth.
• Log explosions (TNT, Creepers, Ghasts, etc)
• Log flint & steel and fire charge usage.
• Log fire igniting blocks
• Log blocks burning up in fires
• Log entities changing blocks (Endermen/Enderdragons)
• Log block movement (Falling sand/gravel)
• Log leaf decay
• Log player interactions
• Log Nether portal generation
• Log blocks moved by pistons
• Log crops trampled by players
• Log snow generated by snow golems
• Log items taken or placed in chests, furnaces, dispensers, etc.
• Log paintings and item frames. (With rollback support!)
• Log entities killed by players (animals/monsters)