system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it not advised to keep the phone plugged in after it has been completely charged?
gpt
Modern chargers stop charging the battery once it reaches 100%.
After this the phone will bypass the battery and use the electricity from the wall socket directly. The charger can become hot if you use a lot of power (similarly as the phone will get hot if you draw a lot of power from the battery).

Some (very much) older chargers, as well as chargers that are defective can heat up beyond a safe point and cause damage. This is likely the reason that this "unplug when fully charged" advise still floats around.

For modern cell phones (using lithium ion based batteries) it's in fact best to discharge the battery as little as possible, as using the battery will over time degrade the battery's life (even if very slowly). Hence it's in fact better to keep your phone plugged in.