a spline is a type of component. just like static mesh components, or light components, you also have spline components, which you can add to actors.
lerp is a common programmer abbreviation for linear interpolation, which means blending from one number to another. Vlerp would be blending from one vector to another, Tlerp would be blending from one transform to another, Rlerp would be for blending between rotations, etc…
this might help:
