You can include different things in a confirmation email, but there are a few things that must be there in every email:
Clear confirmation text for the action they took
Details about that confirmation include the order number, product image, event venue, date, timings, etc.
To get the best out of your confirmation email, you can
Personalize the email for each subscriber
Give them a discount offer or coupon code for the next purchase
Ask for referrals
Add recommendations to upsell or cross-sell