Nodemailer is a Node.js module for sending emails. Here's a quick overview:

1. Transporter: Defines how emails will be sent (via Gmail, custom SMTP, etc.).

   const transporter = nodemailer.createTransport({ ... });

1. Message Object: Specifies email details like sender, recipient, subject, and content (text/HTML).

   const mailOptions = { from, to, subject, text, html };

1. Send Email: Use transporter.sendMail(mailOptions) to send the email.

2. SMTP: Can be configured for custom or service-based email delivery.

3. OAuth2: Option for secure email authentication (e.g., Gmail OAuth).

4. Error Handling: Always handle errors when sending emails.

5. Attachments: Support for including files or images in emails.

Nodemailer is great for automating email notifications in your web applications.