Glossary of Terms Used in Flake8 Documentation

A piece of logic that corresponds to an error code. A check may be a style check (e.g., check the length of a given line against the user configured maximum) or a lint check (e.g., checking for unused imports) or some other check as defined by a plugin.
error class
A larger grouping of related error codes. For example, W503 and W504 are two codes related to whitespace. W50 would be the most specific class of codes relating to whitespace. W would be the warning class that subsumes all whitespace errors.
error code
The symbol associated with a specific check. For example, pycodestyle implements checks that look for whitespace around binary operators and will either return an error code of W503 or W504.
A plugin that augments the output of Flake8 when passed to flake8 --format.
The project Flake8 depends on to calculate the McCabe complexity of a unit of code (e.g., a function). This uses the C class of error codes.
A package that is typically installed from PyPI to augment the behaviour of Flake8 either through adding one or more additional checks or providing additional formatters.
The project Flake8 depends on to provide style enforcement. pycodestyle implements checks for PEP 8. This uses the E and W classes of error codes.
The project Flake8 depends on to lint files (check for unused imports, variables, etc.). This uses the F class of error codes reported by Flake8.
Typically the W class of error codes from pycodestyle.