Is "Hoi" more informal than "Hallo"?
Yes, Hoi is a quick "Hi"
Do "groetjes" and "hoi" mean exact same thing or are they used in different context?
'Hoi' is used as a greeting, and 'groetjes' is used when you're saying goodbye (however, it is not saying goodbye, that would be 'doei'). It's something like: 'Tell Jack I said hi!'.
"Groetjes" is also commonly used to end a letter or email.
Right! Forgot about that one. :)
Thanks a lot! Now it is more clear :)
I think groetjes meaning is similar to "greetings". Like "send my greetings," or "greetings to you."
I typed dag and it was wrong?
Dag is more like a short Goedendag, meaning 'Good day'. It's a little old fashion. 'Dag' literally means 'day'.
It's not 'Aloha'