RAM is an acronym for Random Access Memory. This is the working storage of a computer, where data and programs are stored while we're using them.
A reference argument is another name for a variable from the calling function, rather than an independent variable in the called function. Changing a reference argument therefore does affect the corresponding variable in the calling function.
A register is a storage area that is on the same chip as the CPU itself. Programs use registers to hold data items that are actively in use; data in registers can be accessed within the time allocated to instruction execution, rather than the much longer times needed to access data in RAM.
A retrieval function is a function that retrieves data, which may have been previously stored by a storage function or may be generated when needed by some other method such as calculation according to a formula.
A return address is the memory address of the next machine instruction in a calling function. It is used during execution of a return statement in a called function to transfer execution back to the correct place in the calling function.
A return statement is used by a called function to transfer execution back to the calling function. The return statement can also specify a value of the correct return type for the called function; this value is made available to the calling function to be used for further calculation. An example of a return statement is return 0;, which returns the value 0 to the calling function.
A return type tells the compiler what sort of data a called function returns to the calling function when the called function finishes executing. The return value from main is a special case; it can be used to determine what action a batch file should take next.
ROM is an abbreviation for Read Only Memory. This is the permanent internal storage of a computer, where the programs needed to start up the computer are stored. As this suggests, ROM does not lose its contents when the power is turned off, as contrasted with RAM.
Run time means "while a (previously compiled) program is being executed".