Yes, For every regular language, there exist a minimal DFA and its unique. Here the word, minimal plays the role, otherwise, there can be infinite DFA/NFA for accepting the same language.
Suppose if you have a DFA ( $D_1$ ) for a language L then If you add some unreachable states into the $D_1$ then it becomes, something else, but It can not be minimal. Because in minimal, we remove all the unreachable and redundant steps from the DFA.
I hope you get this.