This is one of the most frequently asked deep learning coding interview questions and answers for freshers in recent times. Operations are nodes that represent the mathematical operations over the tensors on a graph. These operations can be any kind of functions, like add and subtract tensor or maybe an activation function. ALL of these four - tf.constant, tf.matmul, tf.add, tf.nn.sigmoid are operations in TensorFlow. These are like functions in python but operate directly over tensors and each one does a specific thing. While others are straight forward and simple, tf.nn.sigmoid is an activation function, it's a little more complicated, but this function helps learning models to evaluate what kind of information is good or not.