The blockchain is hosted on some servers, there is a protocol to download that blockchain (or parts, and check its validity), and parse the relevant transactions. Interacting with the blockchain is coin specific and there has to be respective endpoints. I may be simplifying this, but the fundamental problem is essentially this.
Can someone give clear answer to the issue of accept crypto payments (bitcoin and ethereum)? If no simple answer can be given, can I be directed to a developer community who would know the answer?