I have seen many places where they say its obligatory to fast after puberty. Is it true or not?
For example they say someone who is 12 doesn't have to fast, but you have to after puberty.
Yes this is true that you have to make fast after puberty. Puberty have two to three conditions. First your menstruation cycle start second the first wet dream and like these. When you become adult then you have to make fast properly for the whole Ramadan.
yes it is true, fast is obligatory after puberty.