What is the basic difference between ROM and RAM?

ROM: "Read Only Memory" - Under normal conditions the content is fixed.

The data is not lost or affected by power being removed.

There are multiple variations with different prefixes depending on how the data is defined or written; from mask ROM where the content is permanently defined during manufacture through fusible link PROM (each bit settable once only) to EPROM, EEPROM and Flash ROM, where the data can be erased and re-written but appropriate procedures.

RAM: "Random Access Memory" - Memory locations can be written or read at any time and (usually) equally fast, but the content is lost if the power is removed.That's normal "working" memory type in computers.

There are again variations in types; Static RAM will hold the content as long as power is applied, without needing complex control circuits. The storage locations are "flip flop" type circuits which hold their state unless forced to change.

Dynamic RAM can have much higher capacities, but the storage locations are just capacitors, which only hold the data for a fraction of a second. 

They need external circuits to continuously perform "refresh" cycles to maintain the content.

Plus various techniques now mostly obsolete - "Core" memory that used thousands of tiny ferrite rings to store individual bits & even "delay line" memory that used mechanical vibrations down a long metal rod, continuously detected, amplifies and fed back in the other end again..

RAM IS TEMPORARY ROM IS PERAMANENT LIKE YOUR BIOS