The COUNTIF function counts cells that meet supplied criteria, and returns a count of occurrences found. If no cells meet criteria, COUNTIF returns zero.
The asterisk (*) is a wildcard for one or more characters. By concatenating asterisks before and after the value in D5, the formula will count the value as a substring. In other words, it will count the value if it appears anywhere inside any cell in the range.
Any positive result means the value was found. By comparing the result with the greater than operator (>) and zero, we force a final result of TRUE or FALSE.