Gulp is a task/build runner for development. It allows you to do a lot of stuff within your development workflow. You can convert sass to css, make HTML templates, Minify of CSS and JS, Images optimization, setting localhost, refreshing page and much more. The kicker for gulp is that its a streaming build system which doesn't write temp files. It's like Pipes in bash. One task flow into another. Gulp could be compared to Grunt in its usage.