Primorsko is a small Black Sea resort town about 50 km south of Burgas, positioned on a narrow peninsula between two bays. It's considerably quieter than the big northern resorts (Golden Sands, Sunny Beach) and has a more local character — popular with Bulgarian families rather than package tourists.
The beaches on both sides of the peninsula are sandy and generally uncrowded compared to resorts further north. The town has a modest centre with restaurants and bars, none of it particularly remarkable, but the setting is pleasant. The surrounding coast — part of the Strandzha Nature Park — is well preserved and worth exploring if you have a car.
A few kilometres north, the Beglik Tash prehistoric rock sanctuary in the Strandzha hills is worth a half-day excursion — an atmospheric Thracian ritual site with giant granite boulders arranged by ancient hands.
Primorsko is a reasonable base if you want a quiet Black Sea holiday without the full resort infrastructure of the northern coast. Sozopol, with its old town and more character, is about 30 km north and worth a day trip.