Learn Italian: Lui mangia e io pulisco il tavolo. - He eats, and I clean the table.

The verb pulire (to clean) belongs to a special group of -ire verbs that add the extra letters -isc- between the stem (pul-) and the normal ending (-o). This happens in the I, you, he/she/it, and they forms of the present tense.

How is the sc in pulisco pronounced?

Because sc is followed by the letter o, it makes a hard sound like "sk" in "skip". If it were followed by an e or i (like in lui pulisce - he cleans), it would make a soft "sh" sound like in "shoe".

Why are the pronouns lui and io used here? I thought Italians usually drop them.

You are right that subject pronouns are usually dropped because the verb ending tells you who is acting. However, we keep them when we want to show a strong contrast. Using lui and io highlights the difference in what the two people are doing: he is eating while I am cleaning.

I have also seen the word tavola for table. Why use tavolo here?