Refer to figure.
In a Lambert Conformal Conic projection, the cone cuts through the Earth at two specific latitudes, called “Standard Parallels”. At these two parallels, the scale of the chart matches the scale of the Earth, i.e. is only correct, because the standard parallels are the same on the globe as on the cone.

Between the standard parallels, the scale contracts (decreases), i.e. the distance on the reduced Earth is greater than the chart distance. Whilst, outside the standard parallels, the scale expands (increases).

Parallel of origin is the latitude exactly midway between the standard parallels, where scale is at its minimum (most contracted) and the cone is parallel to the tangent.