What is a 'TypeError' in JavaScript and what does it generally indicate?

A TypeError in JavaScript occurs when an operation is performed on a value of an unexpected type. It usually signifies that you're trying to call a method or access a property on something that doesn't support it, or that you're passing an argument of the wrong type to a function. Common causes include attempting to call a method on `null` or `undefined`, using an object as if it were a function, or passing a string where a number is expected.