pws stands for "personalized web search." Setting pws=0 asks Google to drop personalization drawn from your signed-in account and search history, so the results reflect the query and location signals rather than your own past behaviour.
It is not a privacy cloak. Location personalization from your IP address still applies, and pws=0 does not undo that — it only removes the account-and-history layer. For an isolated location test you combine pws=0 with an explicit gl, hl, and uule so the place, not your profile, is the variable.
See how pws=0 changes real results: compare Google from any two locations.
Deeper read: Why your keyword has no single Google ranking