HTML math follows general practice in mathematical typesetting by rendering functions, numbers and other constants in an upright font, while variables are rendered in an italic font. You can set particular terms in a bold face, and for chemical formulae, you can force the use of an upright font. Spacing between constants, variables and operators is determined automatically. White space in the markup is used only to delimit adjacent variables or constants. You don't need spaces before or after binary operators or other special symbols, as these are recognised by the HTML math tokeniser.
White space can be useful, though, for increased legibility while authoring.
SUB, SUP Subscripts and superscripts. Also used for limits. SQRT , ROOT For square roots and other roots of an expression. TEXT Used to include a short piece of text within a math element, and often combined with SUB or SUP elements. These elements are used override the default rendering.