when individual characters join together. it is defined in the font. such as fi or ff in writing, or => forming an arrow, or >= looking like the mathematical form. often using when coding, to make multi-character operators look nicer.

Some languages have characters which are really two letters mushed together, like:

ligatures are when you join two or more glyphs into a single one. For instance, instead of having the two characters = and > to form => if you had ligature support you would see ⇒. Some terminals have support to recognize sequences like => (and others obviously) and turn them into their corresponding ligatures (only for display though, the actual file contents remain umchanged)

A feature in my book! 😄