What it means
Gmail's Last account activity is a recent-access view showing access types, times and IP addresses. It can identify a browser or mail client you forgot about, and it can also reveal access that needs investigation. It is narrower than a complete account audit.
A real-world example
A phone's carrier routes traffic through another city, so Gmail displays an unexpected place even though the access type and time match the owner's phone use.
What to do
Open Details at the bottom of Gmail on a computer, compare the record with your devices, and inspect Google Account security events if something remains unexplained.
The distinction that matters
An approximate location is not proof of who held the device. Conversely, a familiar city does not rule out another person. Google says the view includes recent IPs and that POP, IMAP, mobile carriers and fetching services can create surprising entries.
Google's Gmail activity explanation
