Analog vs Digital Examples
Digital is anything that can be analysed with logic or represented without loss of information by a finite number of discrete values.

For example:

Your test score, e.g. 35.333%, is an analog quantity. It can be any value between 0 and 100 with any mathematical fraction.

"Fail" however is a digital quantity since it is either true or it is false.

You can however, convert analog into a digital scale.

By assigning a number of "bits" of true and false states, you can logically give each combination of those "bits" an analog "weight". At that point you can have a circuit, named an Analog-TO-Digital convertor, that examines the analog data and selects the appropriate bit combination that most closely matches the weight you assigned to it. 

If you do that repeatedly either by time, for something like you favourite radio tune, or by X-Y location for an image, you can store a digitized equivalent of that track or picture. 

Note though information is lost in the process of conversion to digital. Since there are a finite number of combinations of the bits, there are only a finite number of values you can store. As such all the original analog values that were in between the weights you assigned are rounded to the nearest value and you can no longer reconstruct the exact original value. 

If you digitized your test score so the digital weights were 1% each, then it would not matter if your score was 35% or actually 34.5%. It would be stored as 35% in either case. The information that you actually got a little less than 35% would be lost.

Note, as James pointed out in the comments, your Grade is a quantized value based on your cumulative scores. As such you get B, B+ etc. which is a digital, or quantized, representation of your actual results.

Addition.

Another way to think about digital is to go back a couple of millenia to basics. 

Can you accurately represent the quantity using fingers, "digits"?



Look at the four fingers on your left hand. Bend a couple down. There are 16 combinations of bent versus straight fingers. Add more hands, and you have more combinations. (Nerdy entertainment: Count from 0 to 15 in binary with just those four fingers..)

If ALL the states of the quantity you are thinking about can be encoded into combinations of a finite number of straight or bent fingers with 100% accuracy, no loss of information, then the quantity is digital. Digital = "Can turn it into fingers".

If you need an extra third of a finger.. it is not.