Quick meaning
A setting that allows your phone or computer to install updates automatically without you having to do it manually.
Think of it like this
Like a subscription service that delivers improvements to your door without you having to order them.
Where you may see this
You may see this inside app stores, app settings, software updates, and install instructions.
Why it matters
Knowing the term helps you understand what an app is asking you to do before you tap, install, or change anything.
Say it simply
Auto-Update means: A setting that allows your phone or computer to install updates automatically without you having to do it manually.