Apache is a free and open-source cross-platform web server software.
Shopify is a subscription-based software that allows anyone to set up an online store and sell their products. Shopify store owners can also sell in physical locations using Shopify POS, a point-of-sale app and accompanying hardware.
Varnish is a reverse caching proxy.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.