What is a Tangent?

In the app below, the line you see is said to be tangent to the circle. Interact with this app for a few minutes and then answer the question that follows.

Note: LARGE POINTS are moveable. Be sure to drag them around!

Note, in the app above, a tangent line has to intersect a circle. Yet what, specifically, does it mean for a line to be TANGENT to a circle? If you're still not sure, check out the app below.

Note: LARGE POINTS are moveable. Be sure to drag them around!