Almost every app is a list of something: messages, products, songs, search results. On the web you render a long list as a long <ul> and let the browser cope. A phone cannot cope the same way, because every row you render becomes real native views that take memory and layout time, whether or not the row is on screen.
React Native 36,878 's answer is virtualization, built into FlatList, SectionList and their shared base, VirtualizedList. This section builds BookNest's catalog with them and measures FlatList against Shopify 175 's FlashList 7,238 on the emulator. The examples run on Expo SDK 57 6,418 , so on React Native 0.86.3; the list APIs are the same in standalone React Native 0.87.1.