To determine whether or not a word is a noun, i.e. person, place, thing, idea, or feeling, ask yourself if it is something you can point to or experience! For example, headache, joy, compassion, frustration, and nausea are "things" you can feel. Abstract nouns (Idea Nouns), according to Quora, "name an idea, quality, or thing you can't see, hear, smell, or taste." Ideas are concepts, i.e. thought (I am smart enough to do my homework), belief (like Democracy, Buddhism), plan (In ten years I'm going to be rich), or opinion (Children perform better in school when they have eaten a healthy breakfast.)
Regarding your sentence: See Spot run!
If you didn't know Spot was a dog, you would still guess it is a proper noun because Spot is capitalized, even though it's not the first word in a new sentence!
Before Spot is the word "see." See is an active verb because it tells us to do something. Run is also an active verb for that reason.
Hope this helps!