In Russian, adverbs answer the question "How?" Как? They are formed from adjectives and always end with an -о. To form an adverd, replace the ending of the adjective (its last two letters) with the -о ending.
Use adverbs only together with related verbs. Adverbs are inflexible. Adjective are used together with nouns and agree with nouns in genber and number.
Noun + Какой?
Verb + Как?