Yes, it's a lazy version of "что" or "чего" in questions.
If "что?" stands on its own, it's probably stands for 'what have you just said', 'what do you want' etc.
Rather slang than a dialectism.
by the way: "чего?" is slightly outdated/rural but still living version of both
(i.e. it's pronounced /ч'во'/ or /чeво?/' but is perceived as more informal than 'что?'. Sometimes it's written as 'чево' or 'чиво', to represent the rural/informal/illiterate/lazy scent. Or even чаво for dialects).
Cf. ничего (not to be cofused with the noun ничто).
'what do you need'-like questions were once formulated with чего (lit: 'of what'):
"Чего тебе надобно, старче?" (А.С. Пушкин, Сказка о рыбаке и рыбке).
But now 'что'-variant vins.
"Cammy!" - "Чё?" - "А ничё. Так ('=так просто'='просто так'=without a particular reason). Чё не спишь-то?."