Indian English is very similar to the British English of shortly before India gained independence from the British Empire (1947). That means it often sounds formal or old-fashioned. The reason for this is because linguistic change occurs almost entirely in places where that language is the first language, and English is only ever a second or subsequent language in India.

There has been some synchronisation with other English locales due to the effects of globalisation, but not a great deal. Beyond that, it does have some deviations from British English as it was in the days of the Empire, mostly due to grammatical misunderstandings becoming common and thus standard, or linguistic patterns from local languages making their way into English; the two examples that spring most immediately to my mind (as an Australian currently in Hyderabad): “very less” instead of “very little”, and a gratuitous “only” suffix where other dialects would either omit it or place it earlier in a sentence.

Concerning fiblye’s point: in cities, you’ll hear a fair smattering of English words when people are speaking their local languages. In rural areas this happens much less.