Am I not seeing the explanation for the notation used in Lab 1 for Week 3?

For example, what does the superscript “T”, as below, represent?

I’m fortunate that I know the element and 2-dimensional coordinate space notation from other sources, but this lab should really be updated with explanations about what those formalities mean. Should not assume that learners know those pieces. There is a lot of notation in linear algebra in general, as well, not to mention different ways of doing things – so Googling that is hard. Thanks!