Linear Link 1D
This iExpression links a 1D property to a slider (or some other 1D property - like audio keyframes). You specify which value the 1D property should have when the slider has its minimum value and which value it should have when the slider has its maximum value. For all other slider values the iExpression chooses automatically an appropriate value (using linear interpolation).
Link to Slider
Don't put a number here. Use the link button to link this to a slider control, an audio amplitude or some other 1D property.
the smallest value of the slider control (or of the audio level or whatever other property you link to)
the largest value of the slider control (or of the audio level or whatever other property you link to)
Value for Min
the value that the property should have when the linked slider has its minimal value
Value for Max
the value that the property should have when the linked slider has its maximal value
If this is enabled, the property will never have values smaller than 'Value for Min' or larger than 'Value for Max', even if the slider that the property is linked to has values smaller than 'Slider Min' or larger than 'Slider Max'.
Create Your Own Little Fuzzy Friends from Aetuts+
In this tutorial the Linear Link 1D iExpression is used to deform the hair of a cute fuzzy creature when it touches the ground. This iExpression is used around 19:32, the entire iExpressions-based creature rigging starts around 11:30.