This is an ongoing education for the new researchers. Aksamitnik said "inflections" but if you are old enough to have studied English grammar, or Latin, we would call them "cases". So in English we have subject, direct object, indirect object, etc. In Czech, it's nominative, accusative, and dative. Latin uses those terms. In English, the only time we change for case is with pronouns. So subject would be "he", direct object would be "him" and possessive would be "his". Czech and French carry this idea out extensively for regular nouns, however. You learn after a while to drop off those endings and look for the root word.
The funniest thing is that accusative (direct object) for Josef is Josefa, leading many a researcher to change gender for a relative. :)