We use Composer for dependency management. Composer enables us to manage the Magento components and their dependencies.
As an integrator, you want to manage each of your Magento core components and third-party components using the Component Manager and System Upgrade.
To do so, you start by creating a Composer project from our metapackage. The metapackage installs each component so it can be centrally managed after installation.

Composer provides you with the following advantages:

Enables you to reuse third-party libraries without bundling them with source code
Component-based architecture with robust dependency management
Manages dependencies to reduce extension conflicts and compatibility issues
Versioned dependencies
Semantic versioning
Supports the PHP Framework Interoperability standard