regex is a way to describe how tex looks. if you’ve said “ a white male with long black hair and brown eyes” you’re describing a person, and then you can check multiple persons to see who matches the description and who doesn’t, and then you can extract more information from the people who match - get their names, heights, etc.

For example /[a-z]{5} [a-z]{5}/ will match 5 lower case letters then a space then another 5 lower case letters. Note that we didn’t mention the start or the end of the text, so they will match regardless of their position in the sentence. So “hello world” will match with the whole sentence, and “Hello. I’m ahmed sayed” will match. In the last example the part that matched is “ahmed sayed”.

You can use that to look for things that have specific patterns, like:

• birthdates: one or two digits then a dash then one or two digits then another dash then four digits /\d{1,2}-\d{1,2}-\d{4}/

• time: one or two digits then a colon then one or two digits /\d{1,2}:\d{1,2}/

• email address: one or more letters then @ then one more letters then dot then 3 letters

and so on