could someone explain to me what it means and what is happening with " SELF.BIASES = ... " and " SELF.WEIGHTS = ... "?

could someone explain to me what it means and what is happening with " self.biases = ... " and " self.weights = ... " ????

I know that The "sizes" list contains the number of neurons in the relative layers of the network. For example, look at the list for [2, 3, 1] so it will be a three-layer network, with the first layer containing 2 neurons, the second layer 3 neurons, and the third layer 1 neuron.

import random
import numpy as np


class Network(object):


    self.num_layers = len(sizes)
    self.sizes = sizes
    self.biases = [np.random.randn(y, 1) for y in sizes[1:]]
    self.weights = [np.random.randn(y, x) for x, y in zip(sizes[:-1], sizes[1:])]