Apple CarPlay is excellent and very intuitive to use.
In the Civic, your iPhone will need to be connected to the system via Lightning cable to the designated smartphone USB port (this must be an Apple certified cable). As said above, very few OEM units support wireless CarPlay. I believe it was only the BMW 5 series up to the end of last year.
You can use CarPlay for:
Messaging (SMS, iMessage and WhatsApp - access to messaging is via Siri dictation and read back, although you get notifications on screen).
Apple Maps navigation.
Third party apps that are CarPlay enabled, e.g. TuneIn Radio, Spotify, BBC iPlayer radio etc.
You have full access to Siri to control all of the above and much more, e.g. voice access to your calendar, weather, news etc. With Siri you can use voice commands in natural language, unlike the built in voice control which requires the use of specific commands.
I have an Apple Music subscription, and being able to tell Siri to play specific tracks/playlists/radio is wonderful. You can even ask to have tracks you like added to specific playlists - all without having to take your hands off the wheel/eyes off the road.
Apple Maps navigation is now excellent, with the most up to date real time traffic info and excellent guidance, including lane assist and speed limit info - I never use the on board Garmin navi.
You can of course use your phone via the car's interface via Bluetooth. You can even select tracks, artists, playlists etc via Bluetooth now. However, once you get used to CarPlay it's difficult to use anything else.
I feel the Civic's OEM head unit gets somewhat unfair criticism on this forum and some reviews, it's really not that bad, and it's ability to support both CarPlay and Android Auto 'out of the box' is impressive. On VW cars you had to pay to activate it until recently, and BMW are turning it into a subscription service.
Have a look at this - the infographics at the top are interesting:
Also, this is an interesting site:
Give it a try and see what you think - you've probably gathered I'm a big CarPlay fan - I would not want to be without it now.