What is an adverb:

Definition:

Adverbs are the words that give us information about how, how often, where, when, in what way, or to what degree an action is taking place. They modify adjectives, verbs, or other adverbs.

An adverb can express time, manner, place, frequency, quantity, certainty, and degree among other circumstances. We’ll give you all the details about the different type in this extremely useful article. 

In German, we place adverbs close to the word they modify. A lot of adjectives can function as adverbs as well.

In short:
A word that can modify or describe a verb, adjective, another adverb, or entire sentence. Adverbs can be used to show manner (how something happens), degree (to what extent), place (where), and time (when).

Example:

• English: Today, I am very happy, as the train departs punctually here.

• Deutsch: Heute bin ich sehr glücklich, da der Zug hier pünktlich abfährt.