Some links to illustrations that may be of interest
Introduction to Convolution
An intuitive introduction of the convolution operation.
Fourier Transform Visualized
An excellent visualization by the YouTuber 3brown1blue.
Geogebra (Causal) Convolution Animation
This interactive Gegebra application visualizes convolution of causal functions. Two convolved functions are g() and h(), and variables u ans v are used as τ is used in the course (depeding on which of the two alternative convolution integrals you chose to use).
The unit step function is called H(t) in this application.