Adverbs are formed from adjectives by adding -ly. Adverbs are used to describe how an action is performed. Common rules for forming adverbs from adjectives include adding -ly to adjectives ending in a consonant, adding -ily to adjectives ending in -y, and changing -y to -ily for adjectives ending in a consonant before -y. Examples are provided such as "beautifully dressed," "walking slowly," and "smiling happily" to demonstrate how adverbs modify verbs. Exercises are then provided to practice forming adverbs from given adjectives and using them correctly in sentences.