cmdline --- This holds the complete command line for the process.
cwd --- This is a link to the current working directory of the process.
environ --- This file contains the environment for the process.
exe --- A symbolic link to the binary which was executed.
fd --- This is a subdirectory containing one entry for each file which the process has open, named by its file descriptor, and which is a symbolic link to the actual file.
maps --- A file containing the currently mapped memory regions and their access permissions.
mem --- The /dev/mem device is the physical memory before any address translation is done, but the mem file here is the memory of the process that accesses it.
root --- Unix and linux support the idea of a per-process root of the filesystem, set by the chroot(2) system call. This file points to the file system root for this process.
stat --- Status information about the process.