man fstab

Each filesystem is described on a separate line. Fields on each line are separated by tabs or spaces. Lines starting with '#' are comments. Blank lines are ignored. The following is a typical example of an fstab entry:

LABEL=t-home2 /home ext4 defaults,auto_da_alloc 0 2

The first field (fs_spec). This field describes the block special device or remote filesys‐ tem to be mounted.
For ordinary mounts, it will hold (a link to) a block special device node (as created by mknod(8)) for the device to be mounted, like `/dev/cdrom' or `/dev/sdb7'. For NFS mounts, this field is <host>:<dir>, e.g., `knuth.aeb.nl:/'. For filesystems with no storage, any string can be used, and will show up in df(1) output, for example. Typical usage is `proc' for procfs; `mem', `none', or `tmpfs' for tmpfs. Other special filesystems, like udev and sysfs, are typically not listed in fstab.
LABEL=<label> or UUID=<uuid> may be given instead of a device name. This is the recommended method, as device names are often a coincidence of hardware detection order, and can change when other disks are added or removed. For example, `LABEL=Boot' or `UUID=3e6be9de-8139-11d1-9106-a43f08d823a6'. (Use a filesystem- specific tool like e2label(8), xfs_admin(8), or fatlabel(8) to set LABELs on filesystems).
It's also possible to use PARTUUID= and PARTLABEL=. These parti‐ tions identifiers are supported for example for GUID Partition Table (GPT).
See mount(8), blkid(8) or lsblk(8) for more details about device identifiers.
Note that mount(8) uses UUIDs as strings. The string representa‐ tion of the UUID should be based on lower case characters.

The second field (fs_file). This field describes the mount point (target) for the filesys‐ tem. For swap partitions, this field should be specified as `none'. If the name of the mount point contains spaces or tabs these can be escaped as `\040' and '\011' respectively.

The third field (fs_vfstype). This field describes the type of the filesystem. Linux supports many filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfs‐ plus, tmpfs, sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more. For more details, see mount(8).
An entry swap denotes a file or partition to be used for swap‐ ping, cf. swapon(8). An entry none is useful for bind or move mounts.
More than one type may be specified in a comma-separated list.
mount(8) and umount(8) support filesystem subtypes. The subtype is defined by '.subtype' suffix. For example 'fuse.sshfs'. It's recommended to use subtype notation rather than add any prefix to the first fstab field (for example 'sshfs#example.com' is deprecated).

The fourth field (fs_mntops). This field describes the mount options associated with the filesystem.
It is formatted as a comma-separated list of options. It con‐ tains at least the type of mount (ro or rw), plus any additional options appropriate to the filesystem type (including perfor‐ mance-tuning options). For details, see mount(8) or swapon(8).
Basic filesystem-independent options are:
defaults use default options: rw, suid, dev, exec, auto, nouser, and async.
noauto do not mount when "mount -a" is given (e.g., at boot time)
user allow a user to mount
owner allow device owner to mount
comment or x-<name> for use by fstab-maintaining programs
nofail do not report errors for this device if it does not ex‐ist.

The fifth field (fs_freq). This field is used by dump(8) to determine which filesystems need to be dumped. Defaults to zero (don't dump) if not present.

The sixth field (fs_passno). This field is used by fsck(8) to determine the order in which filesystem checks are done at boot time. The root filesystem should be specified with a fs_passno of 1. Other filesystems should have a fs_passno of 2. Filesystems within a drive will be checked sequentially, but filesystems on different drives will be checked at the same time to utilize parallelism avail‐ able in the hardware. Defaults to zero (don't fsck) if not present.