B3LYP (Becke, 3-parameter, Lee-Yang-Parr) is a popular hybrid functional that combines the local density approximation (LDA) with the gradient-corrected exchange and correlation functionals. It works well for a wide range of systems but can struggle with predicting properties related to charge transfer and long-range interactions. Also, B3LYP, while widely used and successful in many cases, does not explicitly include dispersion corrections (also known as van der Waals forces).

CAM-B3LYP, on the other hand, includes a correction for long-range interactions. The "CAM" stands for "Counterpoise Corrected for Adsorption Model," and it's particularly useful when dealing with molecules that involve noncovalent interactions, like dispersion forces. This correction accounts for the overestimation of interaction energies that can occur when the basis sets of two interacting fragments overlap.

In a nutshell, if you're working with systems where intermolecular interactions play a significant role, CAM-B3LYP might be the way to go. Otherwise, good old B3LYP should serve you well.

Thank you sir for valueable response.

CAM stands for Coulomb-Attenuating Method.