Numerical differentiation and integration are techniques for approximating derivatives and integrals using discrete data points rather than continuous functions. Numerical differentiation can be done by deriving a formula that approximates the derivative as a linear combination of function values, or by approximating derivatives of discrete data using interpolating polynomials like Newton's forward difference formula. Numerical integration breaks problems into small pieces that can be approximated using simple formulas like the two-point formula to estimate integrals.