If a program is interpreted, its actual human-readable source is read as it is run by the computer. This is generally a slower process than if the program being run has already been compiled.
As opposed to compiled, interpreted means the Prolog system attempts to prove a goal by directly reading the clauses rather than executing instructions from an (abstract) instruction set that is not or only indirectly related to Prolog.
Python is an interpreted language, as opposed to a compiled one. This means that the source files can be run directly without first creating an executable which is then run. Interpreted languages typically have a shorter development/debug cycle than compiled ones, though their programs generally also run more slowly. See also interactive.