Keq is the general term for the equilibrium constant to describe a reaction mixture at equilibrium. It is calculated by the product of the quantities of each/all of the products divided by the quantities of each/all of the reactants:
ie. For reaction aA + bB + cC ⇌ xX + yY + zZ
Keq = [X]^x [Y]^y [Z]^z / [A]^a [ B ]^b [C]^c
Kc is used when the quantities are concentrations expressed as moles per litre.
Kp is used when the quantities are gases expressed as partial pressures.
Ka is the dissociation constant for an acid and is calculated by the product of the concentrations of the dissociated ions (products) divided by the concentration of the undissociated acid (reactant).
ie. Ka = [H+][A-]/ [HA]
Similarly, Kb is the dissociation constant for a base and is calculated by the product of the concentrations of the dissociated ions divided by the concentration of the undissociated base.
ie. Kb = [B+][OH-]/[BOH]