A walkthrough is a camera that follows a path that you define. The path comprises frames and key frames. A key frame is a modifiable frame where you can change the direction and position of the camera.
By default, walkthroughs are created as a series of perspective views, but you can also create them as orthographic 3D views.
A walkthrough path might look something like the following image. The red dots indicate key frames.
A walkthrough path might look something like the following image. The red dots indicate key frames.