The immigration regulations of Uzbekistan require that all foreigners present in Uzbekistan be registered with the local authorities immediately upon arrival in Uzbekistan. You must register within 3 days of arrival in Uzbekistan. If you are staying in a hotel, you will be asked for your passport at check-in and it will be retained for a short period. Hotel staff will complete the registration paperwork and return your passport to you.
If staying in a private house, your host should register you with their local district OVIR (Department of Foreign Travel & Exit (they also deal with the registration of Foreign Citizens)) or on the electronic registration system Emehmon (https://reg.emehmon.uz/)