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.
Google AdSense is a program run by Google through which website publishers serve advertisements that are targeted to the site content and audience.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
StackPath is a cloud computing and services provider.