Japanese particles are short, but they tell you how words relate to the rest of a sentence. Particles such as は (wa), が (ga), を (o), に (ni), and で (de) mark roles such as topic, subject, object, destination, time, and the place where an action happens.
English relies heavily on word order to show who is doing what.
Japanese uses particles to mark relationships between words.
犬が人を噛む
(Inu ga hito o kamu) means
the dog (subject) bites the man (object), no matter where
"inu" or "hito" appear in the sentence.
This guide covers the most common particles and then compares the distinctions that cause the most confusion, especially は (wa) vs. が (ga) and に (ni) vs. で (de).