What is meant by fluctuations and cold variations
The hot changing device is this can be connected and disconnected without turning off the PC. It's definitely something that comes to mind when you think about this with USB devices, and it's actually a great example because we can connect and disconnect as many times as we want without having to switch off the phone in the middle. This includes not only USB paints, but also keyboards, mice, etc.
In contrast, devices cold change are those that we have to turn off the machines in order to connect or uninstall, such as graphics cards or RAM.
Why it is important to know whether the device is hot or swap cold
Of course, we can remove the RAM module from the PC without turning it off, but that can be expensive the party will hang out, and that if we do not cause a a short cycle in doing so, it would create a much bigger disaster. Similarly, the same can happen when we remove a graphics card, when we disconnect power, or when we disconnect a program disk.
For this reason it is important to know which devices are changing and which ones are being exchanged cold. As a general rule, only USB devices change, separately from storage units, but in this case not because of this, but because of the bay where it is installed and because of the motherboard configuration. In other words, if we removed the non-program hard drive, nothing would happen and the PC would still work, but on certain conditions.
An exception: backup devices
Virtual Drives or SSDs do not change per switch, because it depends on what information it contains internally, or in particular, that it contains files used by the system. There are some cases of PCs with external heat exchanger that allow you to hard disk hard without turning on the PC and unplugging anything, but this does not mean that the disks are set for this purpose.
For a hard disk or any other internal storage device to work in this way, it must be configured in the BIOS of the board, as per general rules in the SATA configuration section, such as "hot-swappable" or ESP (Port SATA Port).
This way, we will know that the disk connected to the SATA port configured in the BIOS as it can be deleted, will exchange hot. In any case, we have to make sure that this disk is used as storage, and not to install programs or games because, otherwise, it will act as a cold switch in the sense that when we unplug it with the PC on, there will be things that will stop working even install corruption or system crash.
This, by the way, today can only be configured on SATA or eSATA and AHCI devices (IDE is not compatible, as RAID mode is incompatible).