“Meditation” is an English umbrella for practices that differ significantly. Shamatha cultivates steadiness; Vipassana cultivates insight; Zazen is posture and presence without object; Metta generates a specific quality of heart; Contemplative Prayer rests in relationship with God.
What most forms share: a stable posture, a chosen orientation of attention, and the slow release of the habit of thinking about other things. What changes with practice is not that thoughts stop but that one’s relationship to them loosens.