The Jekyll gem makes a jekyll executable available to you in your terminal.

The jekyll program has several commands but the structure is always:

jekyll command [argument] [option] [argument_to_option]

Examples:
    jekyll new site/ --blank
    jekyll serve --config _alternative_config.yml

Typically you’ll use jekyll serve while developing locally and jekyll build when you need to generate the site for production.

For a full list of options and their argument, see Build Command Options.