An Application Programming Interface (API) is code that is either by itself or part of a larger application that provides a way for other software to communicate with it. For instance, the Drupal API provides methods for modules to hook into the various parts of the Drupal system.

For more detail, see the Wikipedia article for API.

GeoJSON is another format for describing a set of geographical features, based on the JavaScript Object Notation (JSON) standard. It is relatively new, but it has seen a lot of adoption quickly, mostly because it is simpler to create than XML (KML), and JSON has become widely adopted as well for communicating data.

For more detail, see the Wikipedia article for GeoJSON.

Geographical information systems (GIS) are systems focused on capturing, managing, and analyzing all sorts of geographical data. It is a broad term, but it is usually used to describe a complete set of tools that handle all aspects of geographical information.

For more detail, see the Wikipedia article for GIS.

Keyhole Markup Language (KML) is an XML standard, as agreed on by the Open Geospatial Consortium, for describing a set of geographical features. It is often used as a “feed,” or a machine-readable export of data for a web application.

For more detail, see the Wikipedia article for KML and the Wikipedia article for the Open Geospatial Consortium, as well as the section Data Types.

Map tiles or a tileset is a collection of digital images of the same size, specifically named for easy retrieval (usually this name incorporates the zoom level and a coordinate system). When the images are put next to each other in the correct order, this creates a complete map for different zoom levels. For instance, a map of the globe at a very low zoom level would only need a few map images to tile together the world (usually four images), but on a very high zoom level, where one could see rooftops, the set of images to make the whole world could be millions.

Raster data is the idea of storing data as a continuous surface, a grid of pixels. Raster data is most often a digital image or a set of digital images; it can be satellite imagery, or it could be an image of a street map, but the pixels can represent any value. In this format, pixels are used to represent the average of the data that the area the pixel covers.

For more detail, see the Wikipedia article for Raster Data as well as the section Data Types.

A vector, specifically a geometric vector, is a geometric entity that has both length (or magnitude) and direction. The direction is the important part that distinguishes one from a scalar value, which is just the magnitude. For geospatial vector data, this is a way of describing where shapes are on the Earth (for instance, the shape of Lake Superior or the location of the closest vegan restaurant).

For more detail, see the Wikipedia subcontent for GIS Vector Data as well as the section Data Types.

A web service is a broad term used to describe the communication between two applications over the Internet (or any network). For web mapping, this often refers to a web application that provides map tiles or geographical data.

For more detail, see the Wikipedia article for Web Service.

Well Known Text (WKT) is a standard text markup language (a specific way of writing text) for representing vector geometry such as points, lines, and polygons. For instance, a point would be written like this: POINT (30 10). This standard is regulated by the Open Geospatial Consortium.

For more detail, see the Wikipedia article for WKT as well as the section Data Types.