A curl is a tool that can be used to transfer data from or to a server. It supports multiple protocols. According to its man page, the following protocols are supported DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET, and TFTP.
As you can imagine, you can do a lot with these. As you probably figured it out, curl supports proxies, user authentication, FTP upload/download, file transfer resume and many many more.
Here are some examples of using curl:
Download a file:
$ curl -O https://wordpress.org/latest.zip
Download a file to output file by your choice:
$ curl -o wordpress.zip https://wordpress.org/latest.zip
To resume an interrupted download you can use:
$ curl -C – O https://wordpress.org/latest.zip
You can check more useful curl examples here: 15 Tips on how to use curl in Linux.
To install curl, you can use:
$ sudo apt install curl # Debian/Ubuntu
yum install curl # CentOS/RHEL
dnf install curl # Fedora