Why does performance drop when I install a program on a storage device?

Question

Computers

there was also a stupid shameful question

Answer 1

There is no specifics in the question.
To what disk? Where is Windows located? Or on a flash drive?
Such memory is external, but what is the main one?
PC performance will be reduced during any work with files.
I explain with my fingers. You have a relationship with all components when you install the game :
Processor - unzips the files it has read from RAM and copies them to RAM.
RAM (Random Access Memory) - stores unsaved files on board.
HDD (Hard Disk Drive) - Write files to it and read files.
This is if you do not delve further into the depths of architecture and all the little things.

Answer 2

I would google it, but my browser can't figure out what I want from it.

Not surprising, because even I did not understand what is suffering in you (at first glance, the ability to coherently express one's thoughts).
Performance may suffer when installing software on a clogged hard disk due to fragmentation, run "Disk Optimization".
Actions on files and some heavy program running at the same time (including games) of course affect each other and both will run slower.