Adverbs are used to give more detail or modify the meaning of a verb, an adjective, another adverb, or an entire sentence. In contrast, adjectives are used to describe or define a noun or a pronoun. Unlike adjectives, adverbs never change their form.
Some adverbs derive from adjectives, for example:
"Lento" → "Lentamente"
"Incredibile" → "Incredibilmente"
"Recente" → "Recentemente"
Other adverbs don't derive from adjectives and have their own form, for example:
"Bene"
"Male"
"Domani"
Some adjectives are also adverbs, and you can distinguish the difference by their role.
For example "piano" can mean "flat" (una superficie piana), and, as such is variable, an adjective; it also means "softly", invariable, an adverb.