Help adding data plan to new iPad Air

So I bought the iPad Air with wifi+data, but was a little confused when I went into cellular to set up the actual data plan. I see the typical "select a carrier" option, but there is also a "Available Plans from Other Devices" option which shows my iPhone carrier and number. Below this option it says "Add this iPad to an existing iPhone cellular plan".

Is this an option to share my current data plan for my iPhone? Will it just connect the data plan to my Carrier's account? Or will it transfer my phones plan?

I don't have a carrier SIM card so I'm assuming this is an eSIM set up. Just trying to make sure because I use my phone a lot for work and I don't want to knock it offline.