How are weights represented in a convolution neural network?
In convolutional layers the weights are represented as the multiplicative factor of the filters. 



For example, if we have the input 2D matrix in green 



with the convolution filter 



Each matrix element in the convolution filter is the weights that are being trained. These weights will impact the extracted convolved features as 



Based on the resulting features, we then get the predicted outputs and we can use backpropagation to train the weights in the convolution filter as you can see here.