# Paragraph space

I'm currently writing a math document containing equations, theorems, remarks, etc. I find it difficult to understand how LaTeX manages the vertical space between two paragraphs. E.g. when you don't specify anything about the paragraph style, a new paragraph is indented but there is no vertical space between the two paragraphs. Before and after a theorem, there is a line skip. I would like to have a vertical space between two paragraphs too but when I put \setlength{\parskip}{\baselineskip} in the preamble, it messes up the space before and after a theorem.

How does one manage the space between two paragraphs? Should one use two enters, \\ or \par to make a new paragraph? What's the difference between those? And is there a difference between , equation* and align* with respect to the paragraph space?