Fun fact: Most Germanic languages have cases that change words depending on their relation to other words. The words change to tell you what the subject is, what its relationship to the verb is, et cetera.
English does not. We threw them out, because we took from so many different languages that there’s just no room in our grammar structure for cases anymore. Instead, we have tenses, which fill some of the same roles as cases, but it’s a very small overlap. Our syntax covers a little bit more of the gap; most sentences make no sense if you put words in the wrong order. We also have prepositions to denote the direction of the action.
But some words retain their declensions. But they’re so few and far between that they seem like these weird inventions of strict Victorian schoolmasters.
So just remember. We may have eight forms of the verb ‘to lay,’ but German has sixteen forms of the article ‘the.’