Answer: All three create URLSessionTask subclasses but handle data differently.

Task	Best for	Data handling
dataTask	API calls, small responses	In memory
downloadTask	Files, large responses	Written to disk
uploadTask	Sending files/data	Streams from memory or file

Code Example:

// dataTask — API response stays in memory
URLSession.shared.dataTask(with: url) { data, response, error in
    guard let data = data else { return }
    let user = try? JSONDecoder().decode(User.self, from: data)
}

// downloadTask — saves to temp file, survives memory pressure
URLSession.shared.downloadTask(with: url) { tempURL, response, error in
    guard let tempURL = tempURL else { return }
    let dest = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    try? FileManager.default.moveItem(at: tempURL, to: dest.appendingPathComponent("video.mp4"))
}

// uploadTask — send a file
var request = URLRequest(url: uploadURL)
request.httpMethod = "POST"
URLSession.shared.uploadTask(with: request, fromFile: fileURL) { data, response, error in }