The term x/kA is known as Thermal Resistance.

Distance Explanation:

Thermal conductivity is the ability of a material to conduct heat, and it represents the quantity of thermal energy that flows per unit time through a unit area with a temperature gradient of 1° per unit distance.

The thermal conductivity of the material is given as

Q = kA(T₁ − T₂)t/x

Where

T₁ & T₂ = Temperature of plate 1 & 2

x =  Thickness of slab

A = Area of slab

k = Thermal conductivity of the body

t = time through which the heat flow has taken place

Thermal Resistance: It is the reciprocal of thermal conductance. The SI unit of absolute thermal resistance is kelvins per watt (K/W) or the equivalent degrees Celsius per watt (°C/W)

Thermal resistance is given by the formula

Q = x/kA