After spending a day digging into this I wanted to provide what I believe is a slightly more accurate answer. The webpack team has published a useful (and tricky to notice) glossary.
I believe the confusion about chunks and bundles is that the terms can refer to the same thing, but should be used at different points in the webpack process.
webpack glossary definitions
Module: Discrete chunks of functionality that provide a smaller surface area than a full program. Well-written modules provide solid abstractions and encapsulation boundaries which make up a coherent design and clear purpose.
Chunk: This webpack-specific term is used internally to manage the bundling process. Bundles are composed out of chunks, of which there are several types (e.g. entry and child). Typically, chunks directly correspond with the output bundles however, there are some configurations that don't yield a one-to-one relationship.
Bundle: Produced from a number of distinct modules, bundles contain the final versions of source files that have already undergone the loading and compilation process.
(emphasis added by me)
Interpretation
I summarize the difference as: a chunk is a group of modules within the webpack process, a bundle is an emitted chunk or set of chunks.
The distinction is useful when talking about webpack processes as they are occuring. As modules are chunked together, they can change significantly (especially during plugin processing), so it isn't accurate to call them bundles at that point, the chunks may not even be emitted as bundles in the final output! Then after webpack is finished it is useful to have a term to refer to all of the emitted, final files (bundles).
Your example
So for your example
{
entry: {
foo: ["webpack/hot/only-dev-server.js","./src/foo.js"],
bar: ["./src/bar.js"]
},
output: {
path: "./dist",
filename: "[name].js"
}
}- Modules: "webpack/hot/only-dev-server.js", "./src/foo.js", "./src/bar.js" ( + any other modules that are dependencies of these entry points!)
- Chunks: foo, bar
- Bundles: foo, bar
In your example your chunks and bundles have a 1:1 relationship, but this isn't always the case. For example adding source maps would mean you have a 1:2 relationship between a chunk and a bundle.
