Abhisheka (abhiṣeka) is a ceremonial bathing or pouring of a substance over a sacred image or emblem. In Shiva worship it often refers to the reverential bathing of a Shiva linga. Water is common; other substances appear in some regional and temple traditions. The act expresses honour, devotion and the special sacred status accorded to the image in that community.
Descriptions of abhisheka should distinguish an ordinary public explanation from a full liturgical procedure. There is no single ingredient list, order, mantra or qualification that applies to all Shaiva settings. Practical details depend on the actual temple's rules, materials, and the relevant textual or customary authority. This answer does not establish an approved abhisheka sequence.