Can you explain what it means to send data to a server using a POST request?

A POST request is one of the HTTP methods used to send data to a server. Unlike a GET request, where data is transmitted in the URL, POST data is sent in the request body.

This is convenient when you need to transmit large volumes of data, such as a registration form, file upload, or JSON with information.

In practice, sending a POST request on iOS can look like this (using URLSession):

let url = URL(string: "https://example.com/api")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
let parameters = ["username": "user", "password": "pass"]
request.httpBody = try? JSONSerialization.data(withJSONObject: parameters)
request.setValue("application/json", forHTTPHeaderField: "Content-Type")

let task = URLSession.shared.dataTask(with: request) { data, response, error in
    // handle response
}
task.resume()

Thus, a POST request allows sending data to the server for creating or updating resources.