I'm trying to figure out what Rake is for. Here's a dire lions attacks:

2 claws +13 melee (1d6+7) and bite +7 melee (1d8+3)

Here is the description of its special ability, rake

Rake (Ex): Attack bonus +12 melee, damage 1d6+3.

These two other abilities mention rake:

Improved Grab (Ex): To use this ability, a dire lion must hit with its bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can rake.
Pounce (Ex): If a dire lion charges, it can make a full attack, including two rake attacks.

questions:
1) is Rake an attack that can be used at any time, or only during Pounce and Improved Grab?

2) During Pounce, do the two rake attacks replace any of its normal attacks, or does the dire lion get 2 claws, a bite, and 2 rakes?

3) Whats the advantage of using rake in the improved grab case? It seems that the lion can use a claw and get better results- why does it mention that if it wins a grapple check it "can" rake- is that a free attack?

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