A tax is imposed on everyone for general purposes; a special assessment is imposed only on properties that receive a special benefit, in proportion to that benefit. That distinction determines who pays for local infrastructure. It is also the source of nearly every dispute in local development finance. This article explains the special benefit and apportionment requirements and the procedure that supports them. It then covers the impact fee framework and the unconstitutional conditions doctrine that constrains it, tax increment financing and its base year mechanics, and the special district governance rules that permit property-weighted voting in some districts and forbid it in others.