We can find internal and external commands.
Comandos internos fazem parte do próprio shell.
Comandos externos são binários armazenados nos diretórios /sbin, /usr/sbin, /usr/bin, /bin ou /usr/local/bin.
Text typed into the terminal can be divided into three parts, the command, options starting with – or —, and the argument. These divisions must be separated by spaces.
As an example, let’s list the files inside the tmp folder, using a long listing.
ls -l /tmp/