You mean "Jaha". It can mean many things and it is used in many different situations and it also depends on your intonation.
Expressing mild surprise:
- Did you know X and Y are getting married?
- Jaha? (tone goes up at the end because you're excited about the news). In english it would be "Really?". You could also say "Jaså?".
Expressing "i don't care".
- Did you know X and Y are getting married?
- Jaha? Vem bryr sig? (So? Who cares?)
Whe it's not used as a question it could be:
"Oh.. I see"
- X is sad because his wife just died.
- Jahaaa... (usually drawn out, if you say it abruptly it sounds like you don't care)
"So/alright"
- Jaha, vad vill ni göra nu?
- So, what do you want to do now?
- Jaha, då går vi.
- Alright, let's go.