There are literally thousands of Ubuntu programs available to meet the needs of Ubuntu users. Many of these programs are stored in software archives commonly referred to as repositories. Repositories make it easy to install new software, while also providing a high level of security, since the software is thoroughly tested and built specifically for each version of Ubuntu.
实际上，有数千个Ubuntu程序可以满足Ubuntu用户的需求。 其中许多程序存储在通常称为存储库的软件档案中。 存储库使安装新软件变得容易，同时还提供了高级别的安全性，因为该软件已针对每个Ubuntu版本进行了全面的测试和构建。
Ubuntu distinguishes between software that is “free” and software that is not free. For details of Ubuntu’s Free Software Philosophy please see here.
Ubuntu区分“免费”软件和非免费软件。 有关Ubuntu自由软件哲学的详细信息，请参见此处。
The four main repositories are:
-
Main - Canonical-supported free and open-source software.
-
Universe - Community-maintained free and open-source software.
-
Restricted - Proprietary drivers for devices.
-
Multiverse - Software restricted by copyright or legal issues.
四个主要的存储库是：
- Main(核心库)-规范支持的免费和开源软件。
- Universe(社区库)-社区维护的免费和开源软件。
- Restricted(专有库)-设备的专有驱动程序。
- Multiverse(受限库)-受版权或法律问题限制的软件。
The Ubuntu Install CDs contain software from the “Main” and “Restricted” repositories, so if you have no internet connection you can still install software from the CDs. If you have an internet connection you can install software from any Ubuntu repository.
Ubuntu安装CD包含来自核心库和专有库的软件，因此，如果没有Internet连接，您仍然可以从CD安装软件。 如果您有互联网连接，则可以从任何Ubuntu存储库中安装软件。
Reference
- https://help.ubuntu.com/community/Repositories/Ubuntu
