A sales transaction is a single payment process booking. So if a buyer purchases 4 tickets in one booking/sales transaction then it will appear as one entry in the Reports > Sales Transactions page from the admin menu.
Each of your sales transactions in Triniq can be found in the Payments area of the Stripe website's admin or the Activity part of the PayPal admin, depending on which payment gateway you use if not both. If you are using both then log in to both and head back to the Sales Transactions page on Triniq, there will be a link in the Reference URL column that takes you to the correct transaction in the respective payment gateways.
You'll mostly need to use these reports when you are reconciling your accounting.
To view the details of a single transaction click the correct sales transaction link from inside the Reports > Sales Transactions area.