Store data in ROM can not be done easily, but reading data from ROM can be done easily. Usually the program / data in ROM is filled by the manufacturer. Because of this nature, ROM is used to store the firmware (software that are closely related to hardware).
One example is the ROM BIOS ROM that contains the basic programs that manage computer systems / prepared all the equipment / components in the computer when the computer is turned on.
Modern ROM found in the form of IC, just as the medium of storage / memory like RAM. To distinguish it needs to read the text that are listed on his IC. Usually starts with 27xxx number, number 27 indicates the type of ROM, xxx indicates the capacity in kilo bits (not kilo bytes).