On the left-hand side of the location bar, your browser will show you something like :-
Which is entirely correct and incorrect at the same time.
To be precise, what that little label (and the alternative green one) means is that the network traffic is either plain text or encrypted (when you get the green one). In the former case, anyone who can intercept the traffic can see anything that you send to the web site.
So if you are communicating with a web site, and sending any private information you want to make sure you have a little green label.
But that is not the end of the story. Just because a web site has a little green label does not make it secure. Data in transit to and from the site is encrypted so cannot be intercepted, but data at rest on the server is no more safe than it is on a plain text server.
If the server is not maintained properly, it could be successfully attacked, exploited, and all the data leaked. That little label does not say anything about how secure the actual site is.