What means "String"
From AWF-Wiki
In computer science, a string is a set of characters. This may be composed of letters, symbols or numbers. In GIS context, the term string is often used as opposed to numbers.
E.g., a nodata value in a raster-map may be defined as a string (“nan” or “NA”) or as a number (e.g. “-9999“, which is common in ASCII files).
Note that a string may also contain or completely consist of numbers, but these are not recognized as numbers by the computer; which practically means that you can not use them in a mathematic way, e.g. for solving calculations.
See also
- String in Wikipedia
