When you think about the word secure what other words come to mind? Safe? Protected? Here is what Google gave us:

synonyms:
safe, protected, protected from harm/danger, out of danger, sheltered, safe and sound, out of harm’s way, in a safe place, in safe hands, guarded, invulnerable; More at ease, unworried, relaxed, happy, confident “an environment in which children can feel secure”

This is what people need to feel when they visit your website. And now users now have some added help. If you haven’t visited your own website in a while take a second look at the URL in the web browser. You’re going to see one of a few things here.  You’re going to either see a little locked lock, the word ‘secure’, an unlocked lock, or the word ‘not secure’. Either of the last two are not good. Here is an example.
This new alert that users will see, now standard on web browsers, tells them if they can trust this SSL secure website with their private information or not. So if your business accepts credit cards, addresses, contact information or any other info a user might deem private and important this will be a huge red flag for them.
The good thing is this is an easy fix. What you need to do now is purchase a SSL or Secure Sockets Layer certificate. This certificate will authenticate your website online and encrypt information it’s sending and processing to protect it against hackers and online invaders looking to grab any private information that may be of value.

Just in case your are still confused, here is an explanation from the team at TheSSLstore.com explaining the difference secure vs not secure:

HTTP is ancient by computer standards. It’s a protocol for communication and it worked fine for a while. Unfortunately, HTTP is not secure. When you make an HTTP connection with a website that connection is not secure. That means that anyone can eavesdrop on the connection and steal or manipulate any data passed back-and-forth.

HTTPS is secure. When you make a connection with a website the data being sent is encrypted. That essentially makes it worthless to anyone without the corresponding key. Beyond security, HTTPS also blocks ISPs from injecting ads on your website, it is faster and performs better than HTTP and, finally, you have to have encryption in order to use HTTP/2, which is becoming more widely adopted by the day.