Basic mathematical and physical concepts in loop- and path-dependent f
ormulations of Yang-Mills theory are reviewed and set into corresponde
nce. We point out some problems peculiar to these non-local approaches
, in particular those associated with defining structure on various ki
nds of loop spaces. The issues of classical loop equations, differenti
al operators, lattice gauge theory, loop algebras, and canonical quant
ization are discussed in some detail, and the paper concludes with an
extensive list of references.