PayPal is a digital payments platform that enables individuals and businesses to send and receive money, accept online payments, and set up merchant accounts across 100+ countries. It provides SDKs, REST and GraphQL APIs, and client-side JavaScript libraries to integrate payment buttons, checkout flows, and messaging into web and mobile applications. PayPal offers sandbox environments for testing, developer tools and sample apps, and integrations for marketplaces, subscriptions, and payout flows. For developers, PayPal publishes open-source SDKs and examples and provides features like credit messaging, environment switching (sandbox/live), and specialized toolkits (including an MCP-compatible agent toolkit) to support advanced integrations.