What are all these partitions?

The first three are the Windows Critical partitions and there is one hidden which makes 4.

The Image partition contains the OEM factory install components which would be used if you might want to use a Win 10 recovery drive to take your system back to factory, even on a clean drive.

The last one I am not sure but it probably is related to the boot diagnostics and may contain a Bios image used to recover from a Bios corruption situation.

You could shrink the C partition to make a new one.  Having a fairly large C partition can be essential in being able to install future Win 10 upgrades.

A GPT drive can hold up to 256 partitions …. so the number is not that important.

So what I've gathered is this:

EFI: contains data utilized by the UEFI boot loader to initiate the various OS contained on the drive. Keep this partition.

C: contains the OS and files, this is the partition everyone is familiar with. Keep this partition

WinReTool & image partitions: these contain the Windows repair program and the factory reset system image. It is advised to create a back up on a separate usb or dvd. Having the recovery media physically separated from the main drive is better, in the event of a hardware failure. These two partitions can then be removed.

Dell support: the function of this partition is still unknown to me. I assume it's manufacture bloatware. Clarification would be appreciated.

This is what I've identified so far. It was sagested there may be an additional "invisible" partition as well. Have I missed anything?

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@CharlesDaily wrote:

So what I've gathered is this:

WinReTool & image partitions: these contain the Windows repair program and the factory reset system image. It is advised to create a back up on a separate usb or dvd. Having the recovery media physically separated from the main drive is better, in the event of a hardware failure. These two partitions can then be removed.

Dell support: the function of this partition is still unknown to me. I assume it's manufacture bloatware. Clarification would be appreciated.

This is what I've identified so far. It was sagested there may be an additional "invisible" partition as well. Have I missed anything?

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The small recovery partition is what is booted if your system has problems and needs repairing.  The larger image partition contains the factory configuration images, not the Win 10 image.  If you move it to another location, it will not function as designed.  A Win 10 recovery drive, if you check the box to copy system files, will contain everything on the drive to set a new or clean drive back to the same configuration.

The last partition, I believe, is for the boot diagnostics.  If you have never run those you might do so just to see how it works.

I have a 1 TB drive on my system and have no reason to remove small partitions.  You may have some specific need to remove any additional partitions but unless you really need the space, no real reason to.  

The hidden partition is 16 MBs and removing it may mess up the boot due to partition alignment being changed.

If you were to do a clean install of Win 10, you would have 4 partitions.  I will, on most of my systems, remove the original drive to keep safe and install a new drive and do a Clean install.  Any decisions as to what steps you take are totally yours.

The Dell Backup and Recovery (DBaR) program adds an extra Dellsupport partition to the computer's hard disk drive. This partition size varies based on the size storage device, the operating system and the applications preinstalled on the system. The extra partition on the hard disk drive hosts the Dell System Restore image along with the Operating System media image.

This program allows for restoring factory-installed programs that may have become damaged, without having to locate the original program installation media. This can be very valuable if you have preinstalled software such as MS Office as computer companies, in addition to manuals, have discontinued supplying installation disks. I don't know, but this partition may allow the use of the Repair option in Control Panel for preinstalled programs.

Dell Backup and Recovery (DBaR) and the previous OS versions are no longer supported.

DBAR was end of life in 2016.   Windows 7 is end of life in Jan 2020.

<ADMIN NOTE: Broken link has been removed from this post by Dell>

https://www.dell.com/support/article/us/en/04/sln301630/dell-backup-and-recovery-cloud-storage-will-be-retired-on-june-1-2016?lang=en

Is it pretty much the same thing happening here? They have no label but the size look like the OP

(Dell Latitude 7440)

I want to know if I can delete them to gain more space