What is a CSV File? Everything You Need to Know

### Understanding the CSV Format

A **CSV** (Comma-Separated Values) file is a plain text file used to store tabular data (numbers and text) in structured row-and-column format. Each line in the file represents a single data record, and fields within that record are separated by delimiters—most commonly commas (`,`).

Because CSV files are standard plain text, they can be opened by virtually any spreadsheet application (such as Microsoft Excel, Google Sheets, or Apple Numbers), database systems, and text editors.

### Key Characteristics of CSV Files

1. **Plain Text Encoding**: CSV files contain human-readable ASCII or UTF-8 encoded text without binary formatting.
2. **Row Separators**: Each line (terminated by `CRLF` or `LF`) represents a single row.
3. **Field Delimiters**: Fields in a row are separated by commas, semicolons (`;`), or tabs (`\t`).
4. **Quoted Fields**: When a field contains commas, line breaks, or quotation marks, the entire field is enclosed in double quote characters (`"`).

### Official Standard: RFC 4180

While CSV files existed long before formal standardization, **RFC 4180** defines the standard standard specifications for MIME type `text/csv`:
- Lines must be delimited by `CRLF` (`\r\n`).
- The optional header line uses the same format as regular data records.
- Double quotes inside quoted fields must be escaped by prepending another double quote (`""`).

### Why CSV is Popular in Software & Data Science

CSV is the universally supported format for data export and import across database systems (MySQL, PostgreSQL, MongoDB), analytics pipelines (Python pandas, R, Spark), and SaaS tools (Salesforce, Shopify, Stripe).