https://developers.google.com/apps-script/reference/mail/mail-app

Sending a simple email:

Original version:

function myFunction10() {
    MailApp.sendEmail({
        to: 'mymail@gmail.com', // Recipient's email address
        subject: 'Subject of the email',
        body: "Line 1rnLine 2rnLine 3", // Email content
    });

My version with changes or enhancements:

function sendingSimpleEmail() {
    MailApp.sendEmail({
        to: 'darja.suhhanova@gmail.com',
        subject: 'Test',
        body: "Hello,rWorldr!",
    });
}

Sending an email with an attached file:

Original version:

// 1bPpy2Mm7sAffcZwSvuxOooPfrhfEWuE2 - ID of the PDF file stored on Google Drive
    var pdfFileBlob = DriveApp.getFileById( '1bPpy2Mm7sAffcZwSvuxOooPfrhfEWuE2' ).getBlob();
 
    MailApp.sendEmail({
        to: 'mymail@gmail.com', // Recipient's email address
        subject: 'Subject of the email 2',
        body: "Line 1rnLine 2rnLine 3", // Email content
        // Attach the file
        attachments: [pdfFileBlob]
    });
}

My version with changes or enhancements:

function sendingEmailWithFile() {
var pdfFileBlob = DriveApp.getFileById( '1WoONxmLIqfqAAOaxFXZvrWN9ns66VYPnKsk8idhFVAA' ).getBlob();
 
    MailApp.sendEmail({
        to: 'darja.suhhanova@gmail.com',
        subject: 'Test',
        body: "Line 1rnLine 2rnLine 3",

        attachments: [pdfFileBlob]
    });
}