https://thenextweb.com/apps/2018/07/25/heres-what-chromes-new-not-secure-warning-means/

If you’ve updated Google Chrome to version 68, which rolled out this week, you’ll likely begin seeing a ‘Not secure’ warning in the address bar.

That’s to let you know that the site you’re visiting is not HTTPS-enabled, and the traffic is being transmitted over the old, less secure HTTP protocol. That means a hacker could spy on the data you’re sending and receiving from the site in question (such as passwords and credit card numbers), and even hijack the connection to run a phishing scam or redirect you to a malware-laden page.