Does Writing Data to an External HD bypass the main HD?

Usually I always find my answers on my own with google, but I have no idea how to even phrase this for google search terms.

When I download something from the internet or from a device (Such as an HD camcorder), if I select a target folder on an external Hard drive, will it write it directly to the external (bypassing my laptops main internal hard drive)? Or does Windows just write it to a temp file on the main HD, and then when the download is finished, it copies it to the external?

I'm trying to minimize the writes to my laptop's SSD, so I was just wondering.

 

If somebody has the answer, I would also like to know whether the number of writes performed due to manually initiated file transfers are generally outnumbered by the rewrites due to background processes such as caching, eg. windows pagefiles, chrome temporary files.

 

(Assuming Windows is being used.) Downloading from the Internet it'll write to a temp cache file on the internal hard drive then save to the external. Transferring from one external source (camcorder connected through USB) to another external drive connected through USB, it'll be direct bypassing the internal drive.

 

It depends on the browser used.
Some browsers use the temp cache-copy method. Others directly write to destination file as dest-file.tmp and when the download is completed, just rename to dest-file (renaming does not involve data transfer). Or they may just start writing to dest file directly as dest-file right from the start.