This is the 976th most frequent Japanese word.
当たり前
Something obvious, natural, or taken for granted.
Here, 当たり前 (atarimae) is used to highlight a generally accepted standard or expectation—that making an effort is essential for success.
成功するためには努力するのが当たり前です。
To achieve success, it is natural to make an effort.
In this sentence, 当たり前 is used to denote something that is natural or inevitable.
雨が降ったら濡れるのは当たり前です。
If it rains, getting wet is to be expected.
Here, 当たり前 is used to convey that a certain reaction or behavior is justified or reasonable given the circumstances.