WordPress is a free and open source web content management software (CMS) which anyone can download and install on their own server. Using WordPress, you can create blogs and websites ranging from a simple personal blog, a portfolio site, to a full-fledged eCommerce website or a news magazine which serves billions of web pages per month.
Since WordPress is based on PHP and MySQL, it needs a web server to store its data in a database, fetch web pages, and render them dynamically. WordPress supports most of the web servers out there including the Apache Web Server, NGINX, and Microsoft IIS.
There are a lot of ways you can get involved with WordPress depending on your skill set. There are separate teams dedicated to making WordPress even better. Make sure you choose one and join their Slack channel to keep yourself updated and interact with other volunteers.
Apart from becoming a member in one or more of the above virtual teams, you can also attend local WordPress meetups and WordCamps to connect physically with other people working in the WordPress ecosystem.
According to W3Techs, WordPress now powers more than 34% of all the websites on the internet. So, you can imagine the number of people using WordPress to build their websites. But since WordPress is free software, there is no dedicated support team to help you out, only a support page with links to useful articles and a support forum where you can post your questions and get help from theme and plugin developers, fellow WordPress users, and other volunteers.
P.S. Learn how to ask for WordPress support properly and get it from this WPBeginner article.