Where should I store my application files (data, cache, logs, crashes, etc.)

Although I did some research on this subject, I couldn't reach the exact information I wanted. Actually, not exactly disclosed, everyone approached in a different way. For the: Filesystem Hierarchy Standard I should store my files at: - **Temp files:** /var/temp/app_name/* or /temp/app_name/* - **Cache files:** /var/cache/app_name/* - **Config files:** ~/.config/app_name/* - **Log files:** /var/log/app_name/* - **Data files (database, etc.):** ??? **Q1:** Is that the right approach for the recent systems? For the XDG standart that explained here : - **Temp files:** ??? or /temp/app_name/* - **Cache files:** ~/.cache/app_name/* - **Config files:** ~/.config/app_name/* - **Log files:** ??? - **Data files (database, etc.):** ??? I cant understand why we store a cache file in the ~/.cache. It doesn't make any sense to me because there was a built-in cache folder called /var/cache In that case, I'm confused. Everywhere I investigate, there have been different approaches. **Q2:** Where should we put the files (datas, logs, temps, configs, etc.) for a pure Linux distribution (which does not use $XDG) to create applications? **Q3:** Some applications use the Linux structure, but some of use the XDG structure. How do they choose this? According to what situation? Do they use $XDG environment variables if we're using them? According to the above situation, my env | grep -i "XDG" output: XDG_VTNR=1 XDG_SESSION_ID=1 XDG_DATA_DIRS=/home/furkan/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share XDG_RUNTIME_DIR=/run/user/1000 XDG_SEAT=seat0 **P.S:** *I don't know the parts I'm showing with* ???