A numeric constant stands for a number. This number can be an integer, a decimal fraction, or a number in scientific (exponential) notation.1 Here are some examples of numeric constants that all have the same value:
105
1.05e+2
1050e-1
A string constant consists of a sequence of characters enclosed in double-quotation marks. For example:
"parrot"
represents the string whose contents are `parrot'. Strings in gawk can be of any length, and they can contain any of the possible eight-bit ASCII characters including ASCII nul (character code zero). Other awk implementations may have difficulty with some character codes.
[1] The internal representation of all numbers, including integers, uses double-precision floating-point numbers. On most modern systems, these are in IEEE 754 standard format.