German adverbs are not as hard to learn because they are similar to English adverbs. Just like in English, they are used as words to modify verbs, adjectives or other adverbs, as well as used to show time, place, cause, and manner.
These explain things like when, or how long, or how (wo or whoin). For example, an adverb that shows time in German would be "heute" or today, one that shows manner would be: leise or quietly, and one that shows place would be hier or here. You would use them like this: German adverbs before or after a verb, you could say "Ich lese gern" or I like reading, when using one before or after an adjective you could say, "Der Mann da" or the man over there; and if it is modifying a word in your sentence, you could say, "WorÃ¼ber denskst du?" or what are you thinking about?