Those files sit still until something reads them. Two parts of the machine do the reading and the working.
CPU and memory
Also called RAM, Processor
The CPU is the part that carries out instructions, one tiny step at a time, very fast. Memory, or RAM, is the quick short-term space where a running program keeps its instructions and the values it is working on.
Agents test on small examples, so they often write code that loads a whole file into memory because that worked on the sample. At real size it runs out and gets killed. You will notice it as a loud fan, a crash, or a process that vanished.
“This reads the whole log file into memory, and say our logs reach 4 GB. Rewrite it to read one line at a time, then run it under /usr/bin/time -l and show me the peak memory.”