i can't understand when to use regex and when to use delimiter
-Regex
Use this option when your event contains unstructured data like a system log file
-Delimiter
Use this option when your event contains structured data like a .csv file
The delimiters method is designed for structured event data: data from files with headers, where all of the fields in the events are separated by a common delimiter, such as a comma or space. You select a sample event, identify the delimiter, and then rename the fields that the field extractor finds. data that resides in a file that has headers and fields separated by specific characters.
Here it is explained in detail:
https://docs.splunk.com/Documentation/Splunk/7.3.0/Knowledge/ExtractfieldsinteractivelywithIFX
The delimiters method is designed for structured event data: data from files with headers, where all of the fields in the events are separated by a common delimiter, such as a comma or space. You select a sample event, identify the delimiter, and then rename the fields that the field extractor finds. data that resides in a file that has headers and fields separated by specific characters.
Here it is explained in detail:
https://docs.splunk.com/Documentation/Splunk/7.3.0/Knowledge/ExtractfieldsinteractivelywithIFX
What document are you citing?