They're called "strada", similar to what you'd call them in Italian, pronounced with a "š" sound (like the one you'd use to start the word shampoo in English).
When you come to Korčula Old Town, you just do yourself a favour and walk up and down most streets. There are so many interesting things to see and experience, in addition to numerous restaurants, (wine)bars, souvenir shops etc, you will be able to catch a glimpse of real life that still goes on in the strada, and which is still similar to the life that was lead by many people in the past, and which the stone of the Old Town has witnessed. There will be people sitting on their stoops, with a coffee or a glass of wine (depending on the time of day!) in their hand, talking to their neighbors, there will be admiring tourists, there will be wind you will be able to feel differently depending on which side of the town you're on, there will be three-legged cats on top of old barrells... We bring you today a highly subjective Top 5 list, but still, you're much better off not trusting us and taking the time to walk through most of them, and then take a swim below the Old Town!
1) Korčulanskoga Statuta 1214 - named after the Statute from the 13th century, this is the main street, the one where you'll most likely enter the town. Usually it's very, very busy, as it has the view of the Cathedral, several restaurants on both sides, numerous souvenir shops as well as jewellery stores. It will bring you to the main, St. Marko's square, Town Museum, Cathedral, its museum - to the centre of it all!
2) Sv. Roka - once you've gotten to the top, if you want to go straight north to the tip of the Old Town peninsula, the shortest way is to take the other "main street", where there will also be many restaurants (including Adio Mare, one of the oldest restaurants in Old Town, where so many celebrities have visited it's hard to even name them), more souvenirs, a couple of wine bars and a cocktail bar right at the bottom, to help you get over the excitement.
3) Marka Andrijića - when you've climbed to the St. Marko's Square, and are facing North, take a right and go down Marka Andrijića Street. Named after the sculptor who worked his wonders on the Cathedral, the street has everything - a wonderful little "tunnel", basically a walkway between two buildings, crossing over the street right at its beginning, several souvenir shops, couple of restaurants and yet somehow - still a pretty homey feel to it, like you just want to hang out there!
4) Ismaeli - Right to the other side of Marka Andrijića, going to the western side of the island, another one of those straight streets designed to catch the afternoon wind, first of all it has the flag mast on top of it (some say it used to be a pillory in the 16th century; let's just leave it at that and not get into historical discussions over what it really was), which helps you get AMAZING sunset photos when the Sun sets where it should and you manage to catch a photo. It also has one of the loveliest courtyards in Old Town, belonging to a former orphanage - if you pass by it, take a look inside and be amazed!
5) Depolo Street - the one where one of the biggest tourist attractions of Korčula, the House of Marko Polo is located, and where most tourists will gravitate to, in order to see the famous house. If that many tourists are not your thing, just go one street over, to the Don Pavla street, which is home to Lešić Dimitri hotel, so you get to experience at least some of its luxury (and amazing examples of how old-timey buildings can be renovated) and some great souvenir shops.
special feature, no. 6, so much different than the others - The only street in Korčula Old Town that doesn't really have any steps is the officially named Ulica Dobrohotnosti, AKA Ulica filozofa (the Philosopher's Street) - the nickname comes from the fact that you can go deep to your thoughts and concentrate on them, without having to concentrate on those irregular and persistent steps that are present in every other street in the Old Town. There's not much to see in the street itself, but if you find yourself needing to do some deep thinking while in Korčula, you know where to go!