• sudo -s executes in interactive shell, rather than a single command
• With <<< '...' we redirect the content of '...' as input. The idiom <<<word is called a here string, for more details see man bash, search for "Here Strings".
• apt update -y && apt upgrade -y is just an example of two commands chained with &&: first run apt update -y, and only if that is successful, then run apt upgrade -y.

This is different from simply running:

sudo apt update -y && apt upgrade -y

Because in this formulation only the first command (apt update -y) will run with sudo, the second command will run as a regular user.