I often see lte appear on my phone. What does that mean?

I often notice the “LTE” icon appear at the top of my phone screen, but I’m not really sure what that means. Is it related to the quality of the internet connection, my operator’s network, or something else? I would like to understand what LTE means and how it affects the use of my phone for calls, messages and especially internet browsing. Can you explain to me what it is and what are its advantages?