Hindi is a version of northern indian language spoken in india side, while urdu is another version spoken in pakistan but it also exist in india side. If you write in arabic script then, urdu is quite useful but romanized hindi and urdu are easier compared to devanagri or arabic written language if you choose to quickly speak those languages.
Namaste is normal greeting in india, but salaam is quite common too. Other poetic version i guess is adaab which also means hi but i guess it's not used anymore today. try to watch few movies from india or pakistan with english translation and you'd grab some words. Those languages are quite interesting since they had separate development but quite similar. Hindi has Sanskrit words more while Urdu has more Persianized and Arabized words.
Hindi or Urdu could also be understood by Punjabis I believe. But Punjabi tends to be more like regional language with its own written language called Gurumukhi. My dad loves to watch Hindi movies and these movies had penetrated our state since 50's along with Middle East movies from Egypt and Syria but Mid East movies had ceased to be shown in TV while Hindi and Tamil movies still continues to be played especially during special occasions or days, lol