CSV stands for comma-separated values, which means that the comma is the default delimiter for these files. However, they accept other delimiters as well.
CSVs are made of columns and rows and the cell value is arranged in a tabular format. They can come with or without column names and row indices. The primary reasons for a CSV file's existence include manually gathered data, data that's been extracted and downloaded from a database, a direct download from a tool or website, web scraping, and the result of running a data science algorithm.