Concrete nouns are naming words that are used for something that you can physically touch, see, smell, hear or taste. In other words, they are physical things that can be perceived by at least one of the senses.
If you can experience something using at least one of your senses, then it is a concrete noun.
The ugly troll simply loved the taste of snot. Unfortunately, his love of snot had severely impacted his love life.
Snot is a concrete noun. You can see it, you can touch it and the troll can taste it (eugh!)
What’s the difference between snot and spinach?
-The ugly troll would never, ever eat spinach.
So, what’s an abstract noun then?