A RAM drive is a virtual, volatile hard disk created in the computer's memory that provides maximum access speeds. Its contents disappear when you shut down or restart your computer, so it may not provide the benefits of not deleting your temporary files (see above) between sessions. Also, this means that RAM drives should never be used as your output folder, because their contents disappear much too easily.
If you use one it must be large enough to accommodate all the files you write while publishing and you need to be very careful that it does not fill up completely while you are publishing, otherwise you will get errors. Instructions for how to do this go beyond the scope of this documentation. Generally you will need a special software utility to set up a RAM drive.
Never use RAM drives for your output folder!
This is important, so we're going to repeat it: The contents of RAM drives disappear as soon as you shut down or restart your computer. So you should only ever use them for temporary files, never for your output folders!
A RAM drive can improve performance if you only have spinning hard disks
RAM drives are much faster than spinning hard drives so if you don't have an SSD it can be worth it to set up a RAM drive for your temporary publishing files, if you have enough memory. However, an even better solution is to get a modern SSD because that will radically improve the performance of your entire system.
Don't bother with a RAM drive if you have a fast SSD
RAM drives are much faster than spinning hard drives but only marginally faster than SSDs for Help+Manual publishing. If you have a fast SSD, setting up a RAM drive will almost never provide a noticeable improvement, so it is not worth the effort then.