"It tastes good."
Do you mean "What is an adverb"? - If so: an adverb is a POS (part of speech) category, just like noun, verb, adjective etc. It "modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc. (e.g., gently, quite, then, there )."
If you ask "How...?", the answer can be an adverb (How did Forrest Gump run? - He ran quickly). Many POS can be turned into another. E.g. simple (adj) --> simplify (verb) --> simply (adverb). In these cases, they are the adjective/verb/adverb form of the same word (hence the "form"). Some have many forms, some have few or only one.
At the time of posting this comment, Adverbs 1 is the final lession of section 5 here. (They appear earlier though)
No. I'm not asking what an adverb is. I'm asking what is adverb form. Like in english we can turn many adjectives into adverbs by adding -ly.
Obviously there's some sort of rule about making something into an adverb based on the comments I've read. Like god adjective becoming godt in this example making it an adverb. But there's been no tips or notes on such things as how an adjective becomes and adverb.
Det smaker godt. How would I know that godt is the adverbial form of god, when all that's been taught so far is god?