I agree with Paul: the topic is well explained by Prof. Ng in the course material. You might want to watch the video twice and pause + google or ask if a specific term / context is not clear.
Personally, it helped me that I got to know convolution in university from signal and system theory in the course of signal processing and control engineering.
Therefore, maybe this thread and the linked video helps to get familiar with the underlying concept, @Anbu, @Hossain_Piash: How to Calculate the Convolution? - #2 by Christian_Simonis
Please let me know if you have any questions!
Best regards
Christian