That is because there isn't much of a noticeable difference between them.. If you go by size, the fret spacing will be slightly larger if it is a tenor compared to a soprano. I have a tenor and a soprano, and the tenor is slightly longer, but not by much. So it goes from smallest to biggest : Soprano , concert, tenor, then baritone.
But the only way to really see, is by going to a music store. Don't just order online because you have to feel the ukulele... Feel the soul, hear the sound, feel the strings and board.. That is the only way.
NUMBER ONE RULE OF STRINGED INSTRUMENTS IS TO NEVER BUY ONLINE!!!
Okay that was an overstatement. But really, just go to a sam ash or something