[x]Fixed-length block x of certain number of bytes[{] an object start marker, [n] a null value, [21] an integer value, [Hello, World!] a character string
(x)Varialbe-length value x with varying bytes(len) variable-length unsigned integer encoding a length len
<x>Optional, context-dependent value x[[] <data> []] an array block [ ] with content data that may be of varying length
...Memory range of zero or more zeros[...]... an empty array block containing reserved memory, followed by (unused) reserved memory

[x], (x), and <x> are called blocks with content x.