Proton Donor: This term refers to any substance that can donate a proton, or H+, to another substance. In our analogy, this would be like the bucket of water being dumped onto the sponge.
pH Scale: The pH scale measures how acidic or basic a solution is based on its concentration of hydronium ions. It's like rating how wet our sponge is after it's soaked up some water.
Acidic Solution: An acidic solution has more hydronium ions than hydroxide ions (OH-). If our sponge was soaking up more and more water without releasing any, it would be similar to an acidic solution getting more and more hydronium ions.