Imagine you have a bunch of little toys, like Lego bricks or cards, and you want to measure how many of them you have. One way to do that is to count each and every one of them. But imagine you have 100 toys, that would take a lot of time and effort to count them all.
Instead, you can group them up into sets of 10 toys each, and count how many sets you have. That would be a lot faster, right? And you can still get an accurate count of how many toys you have.
In mathematics, we also have ways to group things up to make them easier to count. We call these groups "vectors". And just like with toys, we can measure how long each vector is. We call this measurement the "norm" of the vector.
The norm of a vector is kind of like measuring how many toys you have, but for vectors. And just like with toys, we can use different ways to measure the norm of a vector.
For example, let's say we have a vector that represents the temperature outside. We can measure the norm of this vector using Fahrenheit, Celsius or Kelvin. Each way of measuring the norm will give us a different numerical value, but it's still measuring the same thing: how warm or cold it is outside.
So the field norm is just a fancy way of measuring the length or size of a vector, but in a specific way that is useful for certain types of math problems.