Clarification on ability damage compared to ability drain

[Hobbun]

I just wanted to get a clarification on the difference of ability damage and ability drain, and which one affects the stat directly.

From my understanding, ability damage does not actually lower the stat itself, but as the name implies, does damage where it will give you minuses for every 2 points of damage you take.

”SRD” wrote:

For every 2 points of damage you take to a single ability, apply a –1 penalty to skills and statistics listed with the relevant ability.

Now, ability drain does actually lower the stat, from how I understand it.

”SRD” wrote:

Ability drain actually reduces the relevant ability score.

So what I am trying to clarify, and what I believe, is ability drain the only one that would affect the prevention of a feat if your ability was lowered below the feat requirement? For example, with Power Attack and lowering your Str. below 13?

Or would neither (damage or drain) affect your abilities in that sense?

[Defraeter]

Try this link Ability damage vs drain

Ability damage/penalty:
it is effectively a penalty. What is important is that you can recover/heal naturally (because spell is temporary or with natural healing) or with Lesser Restoration.
Ability damage/penalty doesn't prevent access to feat/spells
1) ability penalty
less powerful damage: it is temporary and you cannot lower ability below 1.
ex: Sell Ray of Enfeeblement
2) ability damage
You need natural healing (or lesser restoration). The damage can lower ability to 0.
Ex: poison

Ability drain/reduce/decrease/drop
You cannot heal naturally and need use of one spell. Some may have a temporary effect but the ability is effectively decreased so prevent access to feat/spells.
1) ability drain
You need a Restoration (or more).
2) ability decrease/...
you need specific spell. The decrease may be temporary but is often a very strong effect.
Ex: feeblemind, bestow curse, Blasphemy (effect "Weakened")

Exceptions:
Some spells have additional effects, which may "contradict" these rules.
Ex: touch of idiocy, it is an ability damage BUT has an additional effect "it may prevent the cast of spells"...

[Hobbun]

Ok, that link and clarification from James Jacobs was what I was looking for.

Thanks!