Variables are placeholders that get replaced with real details when the email is sent. They are how one email works for every customer.
How they work
Type {name} in your message, and the customer sees their own name.
The plugin lists the available variables on the page itself, above each email, so you never have to remember them.
The main ones
{name} The customer’s name.
{site} Your website’s name.
{package} What they bought.
{amount} What they paid.
{date} The relevant date. Depending on the email, this is when they expire, or when they will be charged.
{method} How they paid.
{type} What kind of purchase it was.
{dashboard_url} A link to their dashboard on your site.
{attempt} Which retry attempt this is, for the failed charge email.
Which email gets which
Not every variable works in every email, and it would be strange if it did. There is no amount to show in an email about something that has not been charged.
The plugin tells you which variables are available for each email, right where you are writing it. Use that list rather than guessing.
The payment link emails have their own
If you are on Business or Agency, the payment link emails under Payment links, then Emails, have a different set, because they are doing a different job.
Among them: {payment_link}, {payment_button}, {qr_code}, {order_summary}, {amount}, {expiry_date} and {description}.
The {payment_button} is the one that actually gets you paid, so make sure it is in the payment request email.
Getting it right
Spell them exactly. {name} works. {Name} does not.
Do not invent them. If it is not on the list next to the email you are writing, it will not be replaced, and your customer will receive an email with {something} sitting in the middle of it.
Send yourself a test. The preview uses dummy data, so a test to a real inbox is the only way to be sure.