curl is a tool to transfer data from or to a server, using one of
supported protocols (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP,
IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS,
TELNET and TFTP). The command is designed to work without user inter‐
This is curl.
sudo apt-get install curl means you are going to download and install
curl into your system.
So when you use
sudo and every time you use
sudo you will be asked for your password to ensure that you have permissions to do things for your system
Read this and this for more information about sudo.