What is the difference between full costing and full absorption costing?

The two terms are different names for the same costing technique. Full cost refers to the principle that all overheads, fixed and variable, should be treated as product costs and be absorbed, or allocated, to cost objects. Cost objects can be various items but typically are units of product or service.

This principle is distinct from variable costing in which fixed costs are considered to be period costs rather than product costs, and as such are not allocated to products.

Product costs are used to value stocks of unsold products and cost of production so the selection of basis, full cost or variable cost, will affect the profit of individual products and influence management decisions.