How exactly does Grab work once in a Grapple?

[Azernak0]

I never actually noticed before that Grab deals damage based on the attack that established the hold. Been playing 15 years, missed it 3.5 and Pathfinder until yesterday. Whoops...

I understand how Grab works in order to start a Grapple: Bear bites you. Bear does damage. Bear attacks your CMD. You are Grappled.
Now it's your turn. You fail to get out of Grapple. This is where I start to get a little foggy. Flow chart (https://200e02f3-a-62cb3a1a-s-sites.googlegroups.com/site/pathfinderogc/images/grapple_flow_chart-02.png?attachauth=ANoY7cp75y7ebEU5BBNLJiGu6IT0y35D ZynmvAlHQqNNj1rsBZil8Ctu2Q90zHHrdwCh9mWjGkdluuSdfL j7hgB3oxpy5ZTStH4jgxisNmWWHJzWImeqs7f0AFc4kfibs4A7 8E1GQUnvzuFQhllTZFvkLk9onRdr00V-eO1715TYuAYD13ZeFcn8_3BPIJBq0JIaYFXy28ktT4zdwo0kdX ymXoEuJ-fBE_L_O-2ycNxl4RdAOkD02GE%3D&attredirects=1) shows that the options an attacker has after making a successful maintain grapple check are move, pin, 'nothing', and damage opponent. Does a creature with grab basically deal double bite damage with a successful grapple check if it decides to deal damage instead of pin/move/'nothing'?

What about Greater Grapple?
Standard action bite, deal 1d8+4 damage. Become Grappled.
Move Action maintain grapple, deal 1d8+4 due to Grab, deal 1d8+4 due to Grapple check?

[Psyren]

I never actually noticed before that Grab deals damage based on the attack that established the hold. Been playing 15 years, missed it 3.5 and Pathfinder until yesterday. Whoops...

I understand how Grab works in order to start a Grapple: Bear bites you. Bear does damage. Bear attacks your CMD. You are Grappled.
Now it's your turn. You fail to get out of Grapple. This is where I start to get a little foggy. Flow chart (https://200e02f3-a-62cb3a1a-s-sites.googlegroups.com/site/pathfinderogc/images/grapple_flow_chart-02.png?attachauth=ANoY7cp75y7ebEU5BBNLJiGu6IT0y35D ZynmvAlHQqNNj1rsBZil8Ctu2Q90zHHrdwCh9mWjGkdluuSdfL j7hgB3oxpy5ZTStH4jgxisNmWWHJzWImeqs7f0AFc4kfibs4A7 8E1GQUnvzuFQhllTZFvkLk9onRdr00V-eO1715TYuAYD13ZeFcn8_3BPIJBq0JIaYFXy28ktT4zdwo0kdX ymXoEuJ-fBE_L_O-2ycNxl4RdAOkD02GE%3D&attredirects=1) shows that the options an attacker has after making a successful maintain grapple check are move, pin, 'nothing', and damage opponent. Does a creature with grab basically deal double bite damage with a successful grapple check if it decides to deal damage instead of pin/move/'nothing'?

I think what's confusing you is that Grab doesn't actually add extra damage to your grapple. It's actually the opposite - it adds a free grapple to your damage.

Normal creature with bite: Can either try to bite (standard action) to do damage, or grapple (standard action), the latter doing no damage that round but establishing a grapple.

Creature with bite and grab: Can bite (standard action) to do damage, and then gets a free action grapple, thus letting it effectively do both in the same action. In addition, if it has more suitable natural attacks (e.g claws or tentacles), it can full-attack and get free grapple attempts on all of them.

For both creatures, a grapple leads to the same result on subsequent rounds - they have to maintain as a standard action, and can choose to add bite damage for free if they succeed. The creature with grab has no special damage boost when it comes to maintaining; the ability that grants more damage when maintaining a grapple is Constrict.



What about Greater Grapple?
Standard action bite, deal 1d8+4 damage. Become Grappled.
Move Action maintain grapple, deal 1d8+4 due to Grab, deal 1d8+4 due to Grapple check?

First part is correct.
Second part, Grab does nothing for maintaining a grapple. So the second part becomes: "Move action maintain grapple, deal 1d8+4 due to grapple check." Assuming the move action succeeded at maintaining the grapple, you can use the standard action for something else. If it failed, you will need to use your standard to maintain otherwise you will lose your grip on the foe.

[Azernak0]

There's a single part of Grab that is the source of confusion:

"A successful hold does not deal any extra damage unless the creature also has the constrict special attack. If the creature does not constrict, each successful grapple check it makes during successive rounds automatically deals the damage indicated for the attack that established the hold. Otherwise, it deals constriction damage as well (the amount is given in the creature’s descriptive text)."
Bold is my emphasis.

What in the heck does that mean?