I just want to know if the PC or notebook crashes what can it be.
Hardware failure software failure in pretty much everything
A hardware or software fault. More details are required on a case-by-case basis.
Damaged hard drive (old too)
Power supply (power adapter)
Games could crash (if the graphics card driver is out of date)
after you have formatted and reinstalled the PC (rarely happens but something like that exists, especially if the computer has an old operating system and you want to install a new one)
Can have many causes. Software error, hardware defect, overload. The PC can also crash if the CPU or GPU temperatures are too high. There can be enough reasons for this.
It is also possible that the fan and heat sink are dusty and thus the CPU is overheating. You should regularly remove the dust there.
