Helping people with computers... one answer at a time.
One of the ways that hackers gain access to valuable information is to eavesdrop on internet connections. It's important to know if you're secure.
My computer occasionally tells me that you are about to leave a secure internet connection. It would be possible for others to view information you send. What does this mean.
Most of the time it's an informational message that you can safely ignore. However there are times that it's critically important to know what it means, and whether or not you should be doing something differently.
Someone could be eavesdropping.
Depending on your network and how you're connected to the internet, all computers "close to" each other can actually "see" the network traffic of all the others. For example you could be doing some on-line banking using one computer in your home, but all the data traveling between your computer and your bank could be viewed by another computer in your home. Other computers typically don't listen in, because it's clear that the data is destined for your computer and not another, but software exists that can ignore that.
"Sniffing" software can monitor the data going to and from other computers on the network. This kind of sniffing is particularly easy in WiFi hotspots. When network traffic is wireless, any computer within range of the signal can listen in.
It's kind of like being in a restaurant and listening to the conversation at the table next to you. It's not meant for you, but it's very easy to eavesdrop and listen in.
A "secure" internet connection is one where the data being sent back and forth is encrypted. Only the machine it's destined for knows how to decrypt and read the information.
This is kind of like being back in that same restaurant and listening in, only this time you can't understand a word of what's being said because they're speaking a completely different language. You can listen all you want, it just won't do you any good. Only the two people speaking to each other understand their own language.
"https" connections are encrypted, secure internet connections. "http" connections are not. "http" connections can be sniffed and understood; "https" connections can also be sniffed but the data visible is unintelligible.
In some cases when you're on a page that you visited using an "https" connection, and you click a link that is going to go to a "http" connection, your browser will warn you, and that's the message you're seeing. The issue is that you're leaving a secure connection (https) for an insecure one (http). If the browser didn't warn you it might be easy to miss the fact that this had happened and think that you were browsing securely when you weren't.
It's not at all uncommon to transition from websites accessed by "https" to those accessed with plain "http". "https" is actually a tad slower, and not all information needs to be transmitted securely. There's no reason, for example, to encrypt the contents of this page, and so there's no "https://ask-leo.com". However sites that require security, such as banking or other sensitive services, may be available only via "https".
Linking from one to another is common. The warning is simply that, a warning, so that you know just how secure you are.