A leader in typography is a series of characters, usually lines of dots or dashes, that are used as a visual aid to connect items on a page that might be separated by considerable horizontal distance.
For example, dot leaders are often used in tables of contents to connect section headings with the page numbers on which those sections begin.
This word is pronounced /ˈlidər/ LEED-ər, the same as the everyday word "leader" (person who leads), unlike the typographical term leading (/ˈlɛdɪŋ/ LED-ing), which refers to the use of the metal lead.
These are U+2024 ONE DOT LEADER (․), U+2025 TWO DOT LEADER (‥), and U+2026 HORIZONTAL ELLIPSIS (…), a three dot leader.
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Leader (typography).