Definition - What does Direct3D mean?
Direct3D is a proprietary Microsoft application programming interface (API) framework and part of the DirectX family. It allows developers to create, modify and manage 3D objects, features and services in Windows-based applications.
Direct3D consists of prewritten commands, programs and functions that may be integrated with Windows platform applications.
Techopedia explains Direct3D
Direct3D provides advanced 3D graphic rendering and acceleration services and allows developers to access advanced graphical features and capabilities, particularly for higher end applications, such as games, movies and animation.
Direct3D facilitates access to advanced hardware functions, such as alpha blending, buffering, mapping and special effects. Direct3D accesses all graphical hardware, including video cards, graphic cards, basic processors, random access memory (RAM) and output devices to display 3D objects and images. It also interacts with other DirectX API series and supports 2D graphics.