AddThis is a social bookmarking service that can be integrated into a website with the use of a web widget.
Apache is a free and open-source cross-platform web server software.
Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.