Is it really true that if you learn Hindi or Urdu that you can understand and speak with a speaker of the opposite language? I know the alphabets are different but are the spoken languages really the same?
They're very, very similar except at the highest registers, where Urdu uses a lot of Arabic vocabulary and Hindi uses a lot of Sanskrit.
Technically, they're both forms of the Hindustani language, and linguists classify them as a single language. The split between them is more political than linguistic.
If you want to get really technical, Hindi and Urdu (as well as many other languages of the Indian subcontinent) are part of what's known as a dialect continuum, like the Scandinavian languages.
yeah. They are really similar. It's language continum that has many mutually intelligible dialects starting from magahi, maithli, bhojpuri, audhi, gherwali, pahadi, rajsthani, haryavani. It changes from bengali to punjabi in all these continuum. Hindi and Hindustani words are synonym, only later Hindi became name of standard register. The standard register is called 'Modern standard Hindi' .