wget - The non-interactive network downloader.
Single file download:
wget https://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-9.4.0-i386-xfce-CD-1.iso
Download recursive FTP or HTTP ( can even be used to make a mirror of a website ):
wget -r http://www.some-site.com/movies/
Automatically resumes from where it was interrupted:
wget -c https://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-9.4.0-i386-xfce-CD-1.iso
Speed limit for downloads:
wget https://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-9.4.0-i386-xfce-CD-1.iso --limit-rate=100k
Save file with different name:
wget -O debian.iso https://cdimage.debian.org/debian-cd/current/i386/iso-cd/debian-9.4.0-i386-xfce-CD-1.iso