Noun Cases exist in Arabic. This allows words to be moved around far more freely than English allows. So why would a language allow such movement of words? Well stylistic reasons of course. A person composing the sentence in their head might put the most important info at the beginning. It's all about style. Think about the following sentences: The dog jumped over the house. Jumped the dog over the house. Over the house, jumped the dog.
Notice that the first of those three sentences sounds like completely regular English. Now the other sentences have the words switched around, It doesn't sound like completely regular English, it sounds poetic, in a strange sort of way (It also sounds wrong). Now in Arabic this is done more often than English, because of habit. Arabic also does this (moves words around, keeping same meaning) more often than English because it can afford to without confusing Arabs, or changing the meaning. So how can Arabic do something with words in a sentence that English cannot, simple: noun cases.
Other languages are known for noun-cases, but Arabic uses them in the simplest way. Arabic noun-cases are indicated by vowels Dammah, fatHah, kasrah, and their doubled counterparts (collectively called "tanween"). These marks go at the end of a noun, and are rarely indicated in writing (except for the Quran, and children's books).
Even though Arabic allows more free word order, It is not completely free. There are limits and there is a default way words go in sentences. Most deviation happens in poetry.
What is important is to learn how to recognize noun cases to help get the meaning of the sentence.
Nominative- ُ ٌ Accusative- َ ً Genitive-ِ ٍ