What do the 'async' and 'await' keywords do, and how do they relate to each other?

'async' marks a method as containing asynchronous operations, enabling the use of 'await' inside it; 'await' pauses the method's execution (without blocking the calling thread) until the awaited Task completes, then resumes execution with the result.

async Task<string> FetchDataAsync() {
  HttpClient client = new HttpClient();
  string result = await client.GetStringAsync("https://api.example.com/data");
  return result;
}