Welfare economics is a branch of economics that uses microeconomic techniques to evaluate economic well-being, especially relative to competitive general equilibrium, with a focus on economic efficiency and income distribution.
In general usage, including by economists outside the above context, welfare refers to a form of transfer payment.
Welfare economics deals with the welfare of the people of a country and it is upon the government of that country to take the necessary measures for the welfare of the state and the welfare economics deals with the pareto efficiency, general equilibrium, pareto improvement , etc.
Welfare economics falls under the discipline of Public finance. It’s objective is to utilize microeconomics techniques to evaluate the well-being at an aggregate level. This is to say that welfare economists will use supporting data and history to evaluate the best way to reach pareto optimality.