The sentence is telling you to make sure that your phone's battery is at the maximum capacity for electricity thus, fully "charged". To charge your phone is to plug it into a socket and let the battery take in electricity. Does this make sense to you?
The Language Level symbol shows a user's proficiency in the languages they're interested in. Setting your Language Level helps other users provide you with answers that aren't too complex or too simple.
Has difficulty understanding even short answers in this language.
Can ask simple questions and can understand simple answers.
Can ask all types of general questions and can understand longer answers.
Can understand long, complex answers.
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