The tutor describes the difference between substr() and substring()

Let’s imagine the string variable

var strng_ex=”this_example_string”;

The function substr(4,5) returns 5 characters from the string, starting at the fourth position (which is _, since the first position is 0):

strng_ex.substr(4,5) has value _exam

The function substring(4,5) returns a sequence of characters from the string, starting at position 4, then ending before position 5. Therefore, the value of

strng_ex.substring(4,5) is just _

HTH:)

Source:

www.w3schools.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.