Maybe both.
The line from the phone company connects to the Line port. The
If you were to use just a wireless phone, the base would plug into the phone base unit. But that is not your plan. You want to have multiple wire phones in your house. The wiring, if any, that connects to phones in your house would be connected to the phone port.
It is possible to have these two pairs of wiring on the same wall jack. This would require custom wiring to the jack, and a telephone line splitter to break out the two separate signals.
Understand that you will have to adjust the existing wiring to accomplish this.