## Glossary

This glossary defines terms that appear throughout the CARTO.js documentation.

### A

#### Ajax

Asynchronous JavaScript + XML, while not a technology in itself, is a term coined in 2005 by Jesse James Garrett, that describes a "new" approach to using a number of existing technologies together, including HTML or XHTML, Cascading Style Sheets, JavaScript, The Document Object Model, XML, XSLT, and most importantly the XMLHttpRequest object. More info about Ajax at [Ajax](https://developer.mozilla.org/en-US/docs/Web/Guide/AJAX).

### C

#### Client

Throughout CARTO.js documentation, `client` refers to the object used as an entry point to CARTO.js features.

It's the object used to add your account credentials and to manage layers and dataviews.

More info at [carto.Client]({{site.cartojs_docs}}/reference/#cartoclient)

### L

#### Layer

A layer object is used to visualize geospatial data in CARTO.js. They have a source, where the data comes from, and a style, defining how you want the layer to look like.

They are showed on top of a Leaflet or a Google map. 

[Layer reference]({{site.cartojs_docs}}/reference/#cartolayerlayer)

### P

#### Promise

Promise objects are a standard way for handling asynchronous tasks in Javascript. More info about promises at [Using Promises - MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises).