Im confused with satellite and lte fenix 8 pro

So I get it that I need to send messages and location via satellite as I have had other garmin devices (garmin is god). However I really dont understand derstand how it uses LTE. LTE is where it connects like 3g / 4g. But I have seen no evidence of it doing that. For example if my phone is in aeroplane mode then I need to send messages via satellite. So when I was in IKEA for example I had to wait till I was outside to send messages but the mobile data networks were very strong. 

Please could some fine person explain how the fenix 8 pro USES LTE? I cant currently find any info on it so anyone who helps me to understand this would have my Eternal gratitude. 

  1. If its a dumb question I appologise but it says LTE and Satelite