A computer has millions and which
If they fail to work right
Your plans they will blight
But the experts just say "It’s a glitch."
The very first computers used large valves as electrical switches and these often failed. The coming of the first transistors greatly improved reliability, and integrated circuits involving millions of transistors on a single chip has reduced that possibility of a single transistor failing when being used to almost nothing.
But not entirely. Individual transistors in an integrated chip are now so small that they can be affected by alpha-particles caused by radioactive decay in other components - and by the even more energetic cosmic rays - which becomes important in computers which are to be sent into space.
Where appropriate self-checking and redundant circuits can be used to minimise the possibility of the system becoming non-functional.
If you are interested in the technical side you can find a detailed history and explanation at How Cosmic Rays cause Computer Downtime (pdf).
However for the average users with a pc, laptop or android system, 99.99% percent of gitches are going to be due to software bugs, malicious viruses, or good old human error.