A more thorough explanation:

Definition: A holograph is a document, such as a will or deed, that is handwritten by its author.

For example, if someone writes their own will by hand, without the help of a lawyer or pre-printed form, it is considered a holograph will. The majority rule is that a holographic will need not be entirely handwritten, only the "material provisions" to take into account the popular use of fill-in-the-blank will forms. This means that even if some parts of the will are pre-printed, as long as the important parts are handwritten, it can still be considered a holograph will.

The term "holographic" comes from the Greek words "holos" meaning "whole" and "graphos" meaning "written." It is also sometimes called an "olograph" or "autograph."