Because WordPress is an OpenSource software we can find several places for download, and it does not mean they are official or supported by WordPress.org. So, to start in the world of WordPress development, we need to install the full software from an official or supported site, because, this is the way to keep WordPress fully supported and updated for better performance and security.
The best way to download WordPress is opening this URL https://wordpress.org/download/, and on your right, you will find the latest stable release in two compressed extensions «.zip» or «.tar.gz,» you can download the file type you prefer, both are the same last stable version.
Another way is to open the URL for the latest stable version depending on the compressed file, and they are https://wordpress.org/latest.tar.gz for the Tar.gz file and https://wordpress.org/latest.zip for the Zip.
Also if your intention is to download an old version of WordPress, you can go to this URL https://wordpress.org/download/release-archive/ where you will find the downloadable zip and tar files of WordPress from version 0.72. Remember, it is highly recommended to use always the latest version of WordPress. On many of WordPress releases, they patch vulnerabilities that can compromise your site and server, so, it is important to keep WordPress up to date.
If you want to contribute or you want to follow the constant WordPress development, you can get all the information here https://make.wordpress.org/core/, like Git mirror repositories, Contributors Handbook, and Ticket System for bug tracking.