tmpfs is a temporary filesystem on linux that purely resides in RAM. It can be used to significantly speed up file access or reduce read/write operations on a hard drive.
Arch Linux by default has
/tmp mounted as a tmpfs.
To mount a tmpfs, consult the manual page tmpfs(5). Some simple things are:
mount -t tmpfs -o size=10M tmpfs /mnt/mytmpfs
Since tmpfs is mounted via selecting a type from mount, all mount options apply. See mount(8).