The internet protocol http typically used by most websites apart from online shops is unsecure, the data to and from the server is processed unencrypted. The https protocol is secure and encrypted
As of July 2018 the latest version of the worlds most popular web browser Google Chrome will mark all websites served over http as “Not Secure” in the address bar. Other popular web browser such as Safari and Firefox are sure to follow suit. What does this mean for your website, having “Not Secure” visible in the address bar on every page of your site is likely to deter potential clients from further browsing your site which could result in a loss in revenue.
You can contact your web designer/developer or hosting company and they will be able to assist you, there will more than likely be a cost involved but the benefit as well as mitigating users leaving your site an SSL will also help with SEO and all things being equal will rank your site above a competitor’s that doesn’t have one.