The IPA seems to have developed out of an idea from the 1700s. When shipping ale to India, adding hops to the beer increased the longevity of the brew. Brewers thought that hops preserved the beer for long voyages to hot climates. One London brewer gained attention for his ability to brew this particular style of beer. George Hodgson shipped many casks of pale ales to India from London. However, no one knows for sure when or who coined the name India Pale Ale.
Brewers ferment barley to make India Pale Ales. Depending on the length of fermentation, the tannins may cause some bitterness in the beer, even after adding the hops. While IPAs have a reputation of being bitter and hoppy, not all are. They also tend to be crisper than other beers.