A template method (sometimes just called a template) is a design pattern that defines a template for an algorithm. Instead of coding a full, working solution, a template method implements just the important parts and leaves some details unfinished. It is up to the derived subclasses to implement the missing parts and through that, provide a working algorithm.
A recipe in a cookbook represents a template method. It may say something like take three cups of flour (without specifying where exactly you should get this flour from), put into the oven (without specifying exactly which of your baking tins you should use and what specific mark of oven that should be), serve when cold (without providing any detail about serving plates and table setting), and so on.
As defined by the Gang of Four, the template method implements the important part of the algorithm...