Truth is, you probably won't see Kalman filters even in college - only in grad school.
jee7s already gave you a pretty good basic explanation on what a Kalman filter does, so let me tell you about your options. It's great that you're interested in an advanced topic, and I don't mean to disencourage you, but if you're taking Calculus now, there's a LONG way ahead, and you're probably better off going to college to receive a formal training.
Here's the most likely course route, after Calculus:
Linear Algebra (basic course, I wish someone told me back then how important it would be)
Differential Equations
An Applied Math course (Laplace and Fourier transforms)
Signals and Systems
Classical Control
Linear System Theory
(So-called) Modern Control - state space approach
Intro to Stochastic Processes
Optimal Control (finally you're gonna hear about the Kalman filter)
The last four courses are probably graduate level, depending on where you go to school. As you can see, you're looking at four to six years of college education. It won't be easy, but as a FIRST student you already have a competitive advantage over your future peers: to be curious as hell (and I say that from experience - not too long ago I was in your position).
Let us know if you have further questions.