Difference between Digital signal and Discrete signal
Suppose you have a continuous time analog signal. It is continuous in both time and amplitude. Now when you sample it ,you get discrete samples every Ts seconds. Now you have discrete samples(discrete in time) each of which can take continuous value( in amplitude). This is normally referred to as discrete signal(discrete in time but continuous in amplitude).

Now further when you take this discrete signal and quantise it i.e. say assign each sample which takes continuous amplitude to one of the N discrete quantisation levels of a quantiser, Then your total signal now is a digital signal. So a digital signal is discrete in time and discrete in amplitude.