Alexnet is a image classification model where the input is an image of one of 1000 different classes (e.g. cats, dogs etc.) and the output is a vector of 1000 numbers. The ith element of the output vector is the probability that the input image belongs to the ith class; therefore, the sum of all elements of the output vector is 1.The input to AlexNet is an RGB image of size 224x224 px.