Just like in the 18th Century, IPA has many names and guises from session IPA to imperial IPA. English breweries were sending beer to not just India but several warmer climates for the ex pats who lived their as either civil servants or the upper middle classes. Brewers soon realised that they needed the preservative qualities of hops to maintain the beers condition on the several months long journey.
The volume of hops was increased by about 50% and 'pale beer for the India Market' was created. It had several variations on the name India Pale Ale but ended up being IPA. It was available in the UK whilst we were mostly still drinking porters and brown, maltier ales but it took off when the railways arrived in Burton and it could be transported around the country more readily.
Now, it's a bit of a catch all term for a pale hoppier beer. However. the level of hoppiness and malt varies dramatically. I can think of several mass produced IPA's that are nowhere near as refreshingly hoppy as a pale ale from a craft brewer so I don't think it always follows that an IPA will be the hoppiest beer on offer.
They can range in colour from a pale amber to a straw coloured pale gold with ABV's ranging from 4% to over 7%. The average is around the 5% mark.
A good way of judging how hoppy a beer will be with that pleasing bitterness is to look at the IBU rating. It is complicated though as that shows how many hops are included but as beer is all about balance the amount of malt will affect how bitter the final beer is.
If IPA is your thing or you wish to explore the style further, check out our IPA case here for a mixed collection of 12 IPAs to savour and think how lovely your beer doesn't have to travel six months on stormy seas to get to you any longer.