I'll start from the V1 (There is going to be more but it's from a long time).
V1: It has some characters that are the original (Mametchi, Memetchi, Mimitchi, Kuchipatchi, etc.....) The adult is affected by the care.
V2: It has more characters some are even characters you can't see now. They are affected by care.
V3: Again, it has more characters. They are affected by the way you care. You can go to tamatown!
V4: Something new. It has skill points, which affects the adult. You can go to school, work. You can go to tamatown!
V4.5: New characters, same as above. V5: Something new. You get to raise 3 tamas at once! They are affected by training and bondship. You can go to tamatown!
V5.5: New characters, same as above.
V6(Music Star): Something new. You raise a music star and you can go to school, practice, work. Try to get awards.
V7(Tama-go): The newest one so far. Something new. It has a new house. You can get more NEW characters.