Paypal Braintree Payment Gateway
Paypal is a payment gateway that provides a range of payment processing services, including credit and debit cards, PayPal, and alternative payment methods like Venmo and Apple Pay. Braintree was acquired by PayPal in 2013 and is now part of the PayPal family of products.
Braintree is certified to the highest level of PCI compliance and offers a range of security features, including data encryption, fraud detection, and two-factor authentication. PayPal Braintree offers a simple, flat-rate pricing model with no monthly or hidden fees, and transparent pricing for all transaction types.

Merchant ID
It's a unique identifier assigned to ePRINTit SaaS account by PayPal or other payment processors. It is used to track and manage transactions between ePRINTit SaaS and PayPal.
Private Key
Private keys are used in cryptography to secure data transmissions between two parties. In the context of the PayPal payment gateway, private keys are used to authenticate the identity of ePRINTit SaaS and to encrypt sensitive data such as credit card information during transactions.
When ePRINTit SaaS set up a PayPal account, they were given a unique set of API credentials, which includes a private key. This private key is generated by PayPal and should be kept confidential by the ePRINTit SaaS, as it is used to verify their identity when communicating with PayPal's servers.
Public Key
In cryptography, a public key is used to encrypt data that can only be decrypted by a corresponding private key. In the context of the PayPal payment gateway, a public key is used to encrypt sensitive data such as credit card information during transactions, which is then sent to PayPal for processing.
When ePRINTit SaaS set up a PayPal account, they were given a unique set of API credentials, which includes a public key. This public key can be used to encrypt sensitive data before it is sent to PayPal.