An interpolator uses a t value between 0 and 1 to map or blend values.
LERP and Inverse LERP
In linear interpolation (LERP), if the t value is 0.5, this is equivalent to the mid point value between any two values whether it be numbers, vectors, colors, etc. Unity provides the Mathf.Lerp(start, end, t) method to achieve this where it takes a start, an end, and the percentage (t) between them ((1 - t) * start) + (end * t). The LERP formula is a weighted sum as the starting value has more influence when t = 0 but as t increases, the ending value has more influence.
There is also the concept of extrapolation which goes outside the [0, 1] range to determine a value and is possible when interpolation is not clamped to be within zero and one. The default behavior in Unity is clamped. Inverse LERP exists as well where the t value may be solved by providing a start, end, and value (value - start) / (end - start). The value is first made relative to the start, then scaled by the distance between end and start.
Remap
Sometimes it is necessary to map outside the range of zero and one. How would you map to a different range? Through LERP and inverse LERP of course! Unity does not have a built in remap function but a remap would need to take five values into consideration which are the input min, input max, output min, output max, and the value to map. The inverse LERP would be used on the input range (min, max) and the value to get the t value. Then, LERP can be used on the output range (min, max) and the t value to get the mapped value.