indices kia hy?

daer fellow members kai ap janty hain k indices kia hoty hain, aur bht se log sirf indices pe b trade karty hain.. mery khyal se indices se muraaad kisi country ki tamam companies mil k jo trade volume karti hain usko indices kahty hian jes k pakistan ston exchange ko psx kehty hain? aur usa k indices ko usd indux kaha jata hy.. kia maera concept sahi hy? please correct me if i am wriong?

kissi b currency ka index ye show karta hae k us currency ki maujooda status kia hae aur usky bary induvisulayi taur py bata raha hota hae k ye currency kamzor ho rahi ya strong ho rahi hae jaisa k agr ham USD ka index ki baat karren to agr usd index men doller week hoga to har pair men week hoga.