A library. If you're familiar with pip or npm or the like, you've probably used public repositories. npmjs.org hosts all the free and open source node libraries. But a big org might have a loads of closed and proprietary libraries they need to share and version among multiple development teams or partners. A product like artefactory hosts those kind of libraries for multiple languages and is compatible with the popular package managers.

It's also like a local cache of public repos. That means faster builds, some level of quality control (ie black or white list of safe libraries) as well as protection against things like the leftpad fiasco or 2016.

Anything your build server produces that you want to serve or archive. Binaries, packages, test results, etc.

A package, typically. Like a Maven package for java, a wheel/egg package for Python, a gem package for Ruby, etc.

I would define it as a file that is distributed for use among many decoupled hosts and which is generated from some sort of source input.

Packages/libraries such as those used by NPM and Pip are some examples. It may also be an entire program, an OS package, a virtual machine, a Docker image, even things like PNG images.

Artifactory has tooling to make it easy to integrate into typical build pipelines.

build output