Returns the position of the specified occurrence of the text value {1} found in {0}. An optional parameter {2} may be used ...

Returns the position of the specified occurrence of the text value {1} found in {0}. 
    An optional parameter {2} may be used to specify which occurrence position to return (first occurrence by default).
    
      
{3} is a Comparer which is used to control the comparison. Comparers can be used to provide case insensitive or culture and locale aware comparisons.
The following built in comparers are available in the formula language:
  • Comparer.Ordinal: Used to perform an exact ordinal comparison
  • Comparer.OrdinalIgnoreCase: Used to perform an exact ordinal case-insensitive comparison
  • Comparer.FromCulture: Used to perform a culture aware comparison