In Lambda proxy integration, when a client submits an API request, API Gateway passes to the integrated Lambda function the raw request as-is.
...and:
You can set up a Lambda proxy integration for any API method. But a Lambda proxy integration is more potent when it is configured for an API method involving a generic proxy resource. The generic proxy resource can be denoted by a special templated path variable of {proxy+}, the catch-all ANY method placeholder, or both.
From the article:
In Lambda proxy integration, when a client submits an API request, API Gateway passes to the integrated Lambda function the raw request as-is.
...and:
You can set up a Lambda proxy integration for any API method. But a Lambda proxy integration is more potent when it is configured for an API method involving a generic proxy resource. The generic proxy resource can be denoted by a special templated path variable of {proxy+}, the catch-all ANY method placeholder, or both.