str = ' Salesforce '
Index positions:
S(0) a(1) l(2) e(3) s(4) f(5) o(6) r(7) c(8) e(9)
* substring(start, end)
* Start index inclusive, end index exclusive.
* str.substring(0, 5) # characters at indices 0-4 # " Sales "
* str.substring(1, 5) # indices 1-4 # " ales "
* substr(start, length)
* Start index, then number of characters.
* str.substr(0, 5) # 5 characters starting at index 0 # " Sales "
* str.substr(1, 5) # 5 characters from index 1 # " alesf "
So the expressions that return " Sales " are A and C.