If you understand English, which is duh, you're reading this blog in the first place, so I assume you do, well, anyway, you may have noticed that the doer of the action usually appears first. So the following two sentences have two different meanings.
1. Bob kissed Mary.
2. Mary kissed Bob.
In English, the position of the nouns tell you what the desired action is. So in the above examples, the first noun tells you that it is the one who did the action.
However, it is not always the case that the first noun is the doer of the action. So you can have sentences that have focused elements, or sentences in a different voice, such as the passive, like the following examples.
3. As for Mary, I hate her.
4. Mary was kissed by Bob.
Mary appears as the first noun in the above two sentences, but she is not the one doing the hating, nor the kissing.
Although, one can say that these are not the default sentence patterns of English. However, in other languages, this is not the case. There are languages that can easily mix and move around their nouns. Examples include languages in the Uralic and Altaic family, such as Finnish, Hungarian, and Turkish. East Asian languages such as Japanese and Korean can also do this.
So English speakers may ask: how do they keep track of who is doing what if the nouns can move around? Well, unlike English, these languages that permit scrambling have markers on the nouns that tell the hearer what role this noun has. So the doer of the action usually has a suffix that indicates that it is the doer of the action. The receiver of the action also has a suffix indicating that it is the receiver of the action. So, wherever the nouns appear in the sentence, because of the fact that it is marked for its role, then one can simply scramble things around and it would still make sense.