As with most sports and martial arts, you start learning the movements by going through the motions. In the case of learning with a partner, both of you know roughly what you are supposed to be doing and what is supposed to happen. This is kata (form practice). In addition to the practice you will do almost every class learning and improving your technique in this way, Judo has a number of formal kata.
Seiryoku Zenyo Kokumin Taiiku - Maximum Efficiency National physical education
Kodomo no Kata - forms for children
Nage no Kata - Forms of throwing
Katame no Kata - Forms of grappling
Ju no Kata - Forms of gentleness (or giving way)
Kodokan Goshin jutsu - Self-defense techniques
Kime no Kata - Forms of desiscion (self-defense)
Koshiki no Kata - Forms of Antiquity
Itsutsu no Kata - Forms of "Five"