Nobody is going to be able to explain warnings more than the PM that's automatically sent out to you. Below the reason why is a quick summary of warnings:
"Warnings are different from infractions; they don't actually add any points or count towards your record for getting suspended. We're giving you this warning so you can have a chance to see what you've done wrong and improve before you receive infraction points. If you have any questions about warnings or infractions (or the difference between them), take a look at this thread and feel free to post any questions there. Further information about the infraction system can be found by clicking here (you can also ask any questions you have about the system in that thread.)"
Technically speaking, staff are more likely to be a lot more strict if you have a warning on something than if you don't have any record. So yes, if you don't listen to the warning, you're going to get an infraction. Warnings also contribute to some ban requests that a staff member may post, asking others to consider banning the member for being someone who contributes nothing to the forum and causes a lot of trouble, but those discussions are very, very rare. So technically they do add some sort of quota to a possible ban, but not to the automated points system. They don't contribute anything to that.
I'd actually be more inclined to agree with banning someone who has pages upon pages of warnings for the various things than someone who has half of that in infractions on one or two things.
If you got 25 yellow cards or more, you will be banned permanently
As Ausudraiel or other mod said.
We changed that around the time the new rules got posted, but it was never about yellow cards. Yellow cards don't really mean anything in the matter. If someone has 10 infractions, no matter when they were, they'll be banned automatically upon their 10th infraction for 3 months. Likewise, if they gather 5 more infractions, they'll be booted out for good.
These are the automatic bans: