the.com/landline

means A telephone connected to the network by a physical wire running into the building, rather than through radio signals like a mobile phone.

from Straightforward compound of 'land' + 'line' — a 'line' (wire circuit) that runs over land, as opposed to undersea cables or, later, wireless transmission. The term became necessary only in retrospect: once mobile phones arrived in the late 20th century, people needed a word to distinguish the old wired phone from the new cordless one, so 'landline' rose from a purely technical term into everyday vocabulary almost overnight.