1. Determinant of a matrix
2. Difference between inverse matrix and identity matrix and what are they?
3. Eigenvalues
4. Unitary or orthonormal matrix
5. Diagonal matrix
6. How to compute matrices?

Thank you in advance for answering anyone of them.

I have done some reading and think I have a basic understanding. But if I had to explain it to someone else, I would probably fail, which means I don't understand it well. Please ELI5 this for dummy me.

Let’s say you are 5 years old and your father is 30. The average between you two is 35/2 =17.5.
\ Now let’s say your two cousins are 17 and 18. The average between them is also 17.5.
\ As you can see, the average alone doesn’t tell you much about the actual numbers. Enter standard deviation. Your cousins have a 0.5 standard deviation while you and your father have 12.5.
\ The standard deviation tells you how close are the values to the average. The lower the standard deviation, the less spread around are the values.

this is the easiest explanation that i have read so far:
https://old.reddit.com/r/explainlikeimfive/comments/fsye3q/eli5_can_someone_please_explain_bayesian/
the medical testing/screening example is more confusing to me. but has good direct real wold usage.
anyone think they can explain it well?