Questions

DRAM is a Volatile random-access memory (VRAM).

Volatile random-access memory (VRAM) is random-access memory that retains its information when power is turned on.

Examples of volatile memory are primary storage (typically dynamic RAM, DRAM), and fast CPU cache memory (typically static RAM, SRAM, which is fast but energy-consuming and offer lower memory capacity per area unit than DRAM).

Non-volatile random-access memory (NVRAM) is random-access memory that retains its information when power is turned off.

Examples of non-volatile memory are flash memory (used as secondary memory) and ROM, PROM, EPROM and EEPROM memory (used for storing firmware such as BIOS). 

Wherever on earth we hold a compass, the needle points towards the magnetic North Pole. A compass is a great tool for navigation.

Compass is widely used in aircrafts, ships, military services,...