Left-side person radical — the indexing radical, side-form of 人. Sets the human-action frame for 停: a person halting, parking, lodging, pausing. Same family of 'human action' verbs: 住 (reside), 待 (wait), 仃 (alone), 候 (wait).
Right-side 亭 supplies the sound tíng with no tone shift. 亭 also adds beautiful semantic reinforcement: a pavilion is a roadside resting structure, a place where travelers stop — so 'person + pavilion' = a person at a rest stop = to halt/pause. One of the most pedagogically clean phono-semantic compounds in the script.
