Hi there, do you know much about juggling?  For instance, the most recognizable form of the sport is called toss juggling.
I know nothing about juggling, except what I have seen at the circus. Tell me more about toss juggling.
Toss juggling is all about manipulating the objects.  You can use any type of object such as rings, balls, fruits, or even clubs.
Would knife juggling fall into that same category?
Yes, knife juggling could also be included in this category.  What's nice about juggling, especially toss juggling, is that it can be performed as an exercise, art, or even just a hobby!
Are there other forms of juggling, or just toss juggling?
There are different forms of this skill.  You can use items such as cigar boxes and hula hoops in other forms of this skill. 
I bet hula hoops isn't too difficult. I tried learning with handkerchiefs with I was a child, but I didn't have the patience for it.
That's true.  Certain items are easier to use than other's I'm sure.  I grew up watching my father juggle as well.  It would take a lot of patience to learn to juggle with a chainsaw or a torch.