IPA can also refer to the 'International Phonetic Alphabet'. Coincidentally, it also stands for the organization that built it (International Phonetic Association).
The IPA was developed in the late 1800s as a way to, essentially standardize, spelling. Started by French and English linguists, they attempted to de-conflict different languages using different spelling to realize the same sound speech sound (for example, the 'sh' sound in shoe, was formerly spelled with a 'c' in English, and a 'ch' in French). It is important to note that the IPA isn't a static, immovable thing; changes are made, adding/removing of sounds, and the altering of the typeface of individual letters.