I'm reading a book on vortex methods and I came across the above mentioned terms, however, I don't understand what they mean in mathematical terms. The book seems to be quite valuable with its content and therefore I would like to understand what the author is trying to say using the above mentioned terms in his mathematics. Can someone please tell me what branch of mathematics or what book of mathematics I should read in order to understand these terms? If it helps, I would like to point out that I have a decent understanding of college level calculus. Thanks in advance!