Can you explain what callback hell is?

Callback hell is a situation in programming where, due to a large number of nested asynchronous calls (callback functions), the code becomes difficult to read and maintain. It usually looks like a "forest" of nested curly braces, where each subsequent callback is inside the previous one.

For example, in JavaScript:

asyncOperation1(function(result1) {
  asyncOperation2(result1, function(result2) {
    asyncOperation3(result2, function(result3) {
      // and so on...
    });
  });
});

Problems of callback hell:

• Difficult to track logic and errors.
• Hard to maintain and extend the code.

Solutions include using promises, async/await, or asynchronous management libraries, which allow writing asynchronous code more linearly and clearly.