BASICS

What is a CSV delimiter?

CSV Basics
Simply put, a delimiter is a character that separates values in the data contained in your CSV file so that your program can read them correctly.

Let's say you have contact data that you want to save to a CSV file and import into Google Contacts.

John Smith +18002351234

If you leave it as it is and save it to a CSV file, when you open the file in a spreadsheet, the data will go into one cell. And Google Contacts won't understand what kind of data you want to enter into the system at all.
Now separate the data with a comma. Like this:

John,Smith,+18002351234

Let's save the CSV and open it in a spreadsheet. The data now looks like a table where you can label your contact's First Name, Last Name, and Phone number.
The comma is one of the most common delimiters, as suggested by Comma Separated Value. However, there are other delimiter options as well. This often depends on regional variations in the use of the comma. For example, in Europe, the default delimiter is most often a semicolon, since commas are used to separate decimal fractions (e.g.in currency).

The most common delimiters are:

semicolon
tab
pipe (vertical bar)
space

The presence of a comma within values or text is bound to cause an error if the comma is used as a delimiter at the same time. Sometimes, when no other substitute can be used, the text has to be enclosed in quotation marks, then the spreadsheet or other program, where you import data, will ignore the comma as a delimiter, but that's a different topic for discussion. In any case, if you can't use a comma as a unique delimiter, choose something else.

To summarize, a delimiter in CSV is a character (comma or another) that separates the data in your file into separate values. Or in another way of saying and going back to tabular data, it divides rows in your CSV into columns.