Does permission_level (_self) means that only contract can use this method?

Question

If yes, then how do I make sure that anyone or any specified address can call a method? If not then what is the usage of permission_level (_self ...)?

 action{
    permission_level{_self, "active"_n},
    inf_account,
    "bet"_n, memo}
}.play();

Answer 1

Correct, it means only the account on which the contract resides can call this action. In general, _self refers to the instance of eosio::name that contains the account name where the contract resides