学 (xué): To study or learn. The character pictorially represents a child (子) under a roof, symbolizing a place of learning or school.
习 (xí): To practice, review, or a habit. The character originally depicted feathers (羽) over the sun (日), symbolizing a baby bird repeatedly practicing flying. Crucially, this is also the surname of China's leader, Xi Jinping (习近平).
强 (qiáng): Strong, powerful, to strengthen.
国 (guó): Country, nation, state. The character is a “pictophonetic compound,” showing a boundary or enclosure (囗) around jade (玉), symbolizing the precious territory of a nation.
The characters combine to form two ideas. The literal one is `学习 (xuéxí)`, “to study,” and `强国 (qiáng guó)`, “to strengthen the nation.” However, the politically charged meaning comes from the pun on `习 (xí)`, making the entire phrase a call to action to study President Xi's ideology in order to make China strong.