01In plain English
OAuth is the standard that lets one app get limited access to your account on another, without you handing over your password. When a tool asks you to "connect your Google account" and shows a list of what it wants to access, that is OAuth.
02Why it matters when you are choosing
It is how most tools and AI agents reach your email, calendar or files. The permissions you approve on that screen decide what the tool can read and change, so it is worth reading before you click Allow.
03What to check
Ask the vendor
Read the permission list before approving. Check you can see and remove connected apps later from your account settings.