Substring

Returns substring starting from the character specified by startIndex, with optionally limited length.

Substring("Central and Southern Asia", 13, 5) → "South"
Substring("555000", 3, 4) → 5000

Substring(string, startIndex, [length])

string - A text value
startIndex - Start index to search after. The start position is 1-based, not 0-based
[length] - [optional] - length of the returned substring