Lerp is the procedure to interpolate between two vectors with a specified weight. An example below
float weight; // the weight for lerping vec2 input1, input2; // the inputs to lerp between vec2 lerpResult = input1(1.0-weight)+input2(weight);
In GLSL it’s named mix( genType, genType, float ) instead of lerp which can be misleading. But when testing, it actually works to use lerp instead of mix in GLSL shaders when running them on a Nvidia GeForce 8800GTS although it’s not recommended.
Here’s the OpenGL GLSL quick reference guide which contains all functions you can use inside of a shader (and much more).