Adverbs are words that modify a verb, an adjective or another adverb. Adverbs of manner usually modify a verb; they describe how the action is being performed. Let's look at some examples:

El enfermo estaba comiendo muy despacio.
The sick man was eating very slow.

No solamente come más que tú, también come más rápido que tú.
Not only he eats more than you do; he also eats faster than you.

Tus buenas acciones hablan muy bien de ti.
Your good actions speak well of you.

Some adverbs are formed by adding -mente (-ly)to an adjective:
Adjective ---------------> Adverb

tranquilo (tranquila) - tranquilamente

último (última) - últimamente

ligero (ligera) - ligeramente

Nyscelle está felizmente enamorada.
Nyscelle is happily in love.

La dramática caída del precio del petróleo influyó profundamente en nuestras decisiones.
The dramatic fall of petroleum prices influenced our decisions deeply.