How to unravel the purpose of hidden directories by looking at .gitignore?

Question

git

Walking around https://github.com/github/gitignore/ (typical .gitignore) and trying to understand the thoughts of the project technologists. I'm trying to determine the purpose of hidden directories at https://github.com/github/gitignore/blob/master/Ye... ( .gitignore of the yeoman project).
Help unravel the purpose of the build/ and dist/ directories from .gitignore:

node_modules/
bower_components/
*.log

build/
dist/

Answer 1

node_modules/ - NodeJS modules
bower_components/ - Bower modules
*.log -
build logs/ - Probably temporary, for building.
dist/ - compiled and ready files for production