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# Glossary

There are a few commonly-overloaded terms which refer to specific things in the LIT APIs and codebase:

- Component, a backend component in Python. Includes things like counterfactual generators, metrics classes, UMAP and PCA implementations, and salience methods.

- Element, a Web Component or another HTML element. The `client/elements/` folder contains many custom elements used for visualizations and parts of the UI, but which are not full-fledged LIT Modules.

- Example or Datapoint, an element of a dataset - the things that we feed to models and get predictions back.

- Instance, a specific implementation of LIT (e.g. a demo.py binary) or server job running the former.

- LIT, the Learning Interpretability Tool. Always fully capitalized, sometimes accompanied by a 🔥 emoji. Pronounced “lit”, not “ell-eye-tee”. Formerly known as the Language Interpretability Tool.

- Lit, the web framework consisting of lit-element and lit-html and maintained by the Polymer project. LIT is built on this framework, but the naming is coincidental (we like it, of course).

- Model, a machine-learning model that we’re exploring or debugging with LIT. Doesn’t need to be a single neural network; could be a pipelined or composite system, and may be hosted remotely.

- Module, a frontend visualization module (see Frontend Dev Guide). Strictly speaking, this is something that inherits from LitModule, renders a part of the UI, and interacts with the frontend framework. Usually found in `client/modules/`. All modules are elements, but not all elements are modules.

- Potato (noun or verb), a frontend error. See potato.io.

- Server, the Python backend. A WSGI application that provides a handful of HTTP endpoints to serve models, datasets, and other components.

- Service, a part of the frontend framework that handles state and provides helper methods. Most of these are global singletons, with the notable exception of SelectionService which is duplicated when in example-comparison model.

- Slice, a set of examples from a dataset. Often created by Faceting along a specific feature.

- Widget and Widget Group, elements of the frontend layout. A Widget is a thin wrapper over a Module, and a Widget Group contains one or more widgets along with header bars, resize, and minimize/maximize controls - roughly, like a regular GUI window. Sometimes we refer to a widget or a widget group as a Panel.