The developers of the Raspberry Pi project announced the beginning of the formation of 64-bit assemblies of the Raspberry Pi OS (Raspbian) distribution, based on the Debian 11 package base and optimized for Raspberry Pi boards. Until now, the distribution has only provided 32-bit builds that were unified for all boards. From now on, for boards with processors based on the ARMv8-A architecture, such as Raspberry Pi Zero 2 (SoC BCM2710 with CPU Cortex-A53), Raspberry Pi 3 (SoC BCM2710 with CPU Cortex-A53) and Raspberry Pi 4 (SoC BCM2711 with CPU Cortex -A72), separate 64-bit assemblies began to form.
For older 32-bit Raspberry Pi 1 boards with an ARM1176 CPU, an arm6hf assembly is provided, and for newer 32-bit Raspberry Pi 2 and Raspberry Pi Zero boards with a Cortex-A7 processor, a separate armhf assembly is prepared. Moreover, all three proposed assemblies are compatible with boards from top to bottom, for example, the arm6hf assembly can be used instead of the armhf and arm64 assemblies, and the armhf assembly instead of the arm64 assembly.
Source: opennet.ru