Can you explain what is meant by the term 'body' in the context of HTTP requests?

In the context of HTTP requests, the term "body" refers to the part of the message that contains data transmitted from the client to the server or vice versa.

In requests such as POST or PUT, the body may contain form data, JSON, XML, or other formats that the server needs to process.

Example: when submitting a form with user data, the request body will contain that data.

In iOS, when working with URLSession, the request body is set through the httpBody property of the URLRequest object:

var request = URLRequest(url: URL(string: "https://example.com/api")!)
request.httpMethod = "POST"
let json = ["name": "Ivan", "age": 30]
request.httpBody = try? JSONSerialization.data(withJSONObject: json)

Thus, the request body is the data transmitted along with the HTTP request, different from headers and URL.