Short answer
REST and SOAP are two styles of web API. REST APIs use simple web requests and usually JSON, and are the default for modern integrations. SOAP APIs use a stricter XML-based contract and are common in older enterprise systems. Salesforce supports both, plus Bulk and streaming APIs.
REST vs. SOAP API explained
REST is lighter, easier to work with and well supported by modern tools. SOAP defines operations in a formal WSDL contract, which some legacy and financial systems still require. The style of API a system offers affects integration effort and the tools you can use.
Salesforce is retiring some older SOAP-based login methods, so integrations that authenticate the old way need updating to OAuth.
How Vantage Point helps: we assess the APIs your systems offer and choose the integration approach and tools that fit.
Frequently asked questions
Is REST better than SOAP?
REST is simpler and more common for new integrations. SOAP is still appropriate when a system requires its formal contract and features.
Is Salesforce retiring the SOAP API?
Salesforce is retiring the SOAP API login() method for authentication, not the whole SOAP API. Integrations should move to OAuth-based authentication.