Numerical columns contain numbers. The defining aspect of numerical data is that the numbers have an order and you can apply a variety of mathematical computations to them (average, sum, etc.) The actual values may follow a specific format, such as being rounded to 2 decimal digits and remaining between min/max bounds.
For example, you might be storing product purchase amounts (USD) with 2 decimal digits. You might be storing the ages of your customers as whole numbers that must be 18 or above.
If the data is stored a integers, it does not mean it's necessarily numerical. For example, HTTP response codes such as
404, etc. are stored as integers but they are distinct categories. They cannot be combined or averaged.