An essential oil is a concentrated oil containing volatile aroma compounds from a given plant. An oil is “essential” in the sense that it carries a distinctive scent, or essence, of the plant. Essential oils do not as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances.
Certain essential oils (such as lavender) are antiseptic in nature. Some of them have lipids that the skin can use efficiently for hydration (avocado, for instance). Oil itself doesn’t clog your pores. Dried skin can become trapped in oil if the oil in question is dry-ish and becomes gummy, which can lead to pore-blocking, but a fairly pure oil won’t clog pores in and of itself.
Things to do to keep pores from blocking:
4. Moisturize every day, making sure your moisturizer is not too heavy for your skin type and has a sunscreen in it. (Exfoliating makes skin even more sun sensitive, as it has removed the outer, tougher layer of your skin.)