Tethering is when you turn your smartphone into mobile WI-FI Hotspot and share your phones 4G/5G data connection.
Once you've turned turned tethering on, any device with a wireless connection can connect to the Internet via your smartphone's connection.
You can also upload/download your jobs whilst being tethered to the internet, however please note in some bad signal areas when you only have maybe 1 or 2 bars maximum the jobs may struggle to upload. Therefore I would always check your bar signal before trying this option.
On an iPhone to switch your personal hotspot on you will need to go to
SETTINGS > PERSONAL HOTSPOT > TOGGLE TO SWITCH ON
Please note if it is the first time connecting your device to your iPhone data you may need to enter the Wi-Fi password within the personal hotspot screen which is normally created by yourself.