Brackets
Brackets are squarish symbols which are somewhat common in prose (indicating an insertion in a quotation, or a footnote), though less common than the parenthese. They are also heavily used in mathematics, and as an uncommon emoji.
Brackets are not all that hard to design at all. They can be made from one side of a capital ‘I’, stretched to the dimensions of the parenthese. Oftentimes the bracketing (no pun intended) of the serifs is made more horizontal to give the bracket character a more shelf-like shape. The stem of a bracket is thinner than a normal stem, but it is usually thicker than the vertical bar and the hairline characters. Brackets, while resembling them, are not hairline symbols.
Braces
Braces (sometimes called “French curly brackets”) are a third type of parenthetical character. Braces are not naturally occurring glyphs. They have no usage in any form of writing, except as a math symbol used to denote sets such as x = { 1, 3, 5, 6 }. The only reason they even made it onto the standard keyboard is because computer programmers make heavy use of these glyphs in their code (which should be set in monospaced type anyway).
Braces are difficult to describe. The best way to learn how to draw them is to look at examples from existing typefaces. Braces are also perfectly symmetrical (a rarity in type design), so you can draw the top half and just mirror it to make the bottom half.
