Elementary Stream
在MPEG－2中，包含经过编码的图象、声音或数据的比特流称为基本流ES（Elementary Stream），它只包含一种类型的数据（音频、视频或者字幕），我们常说的“音频”、“视频”或者“比特流”所指的就是Elementary Stream，其的格式一般只由所包含的数据决定（比如视频的codec）。

Packetized Elementary Stream
ES经打包后就成为包基本流PES（Packetized Elementary Stream），它可以和另外1个PES合成1个传输流TS。每个PES都被打包成一个个188byte长的TS数据包。需要指出的是，传输流TS并不是由节目流PS组成的，而是由PES复接成的。1个TS可以包含几个独立的节目，其中的每个PES都带有一个包识别符PID（Packetized Identifier），这样，一个特定节目的所有TS包就可由PID从传输流中提取出来。同时，可以向现有的传输流添加新的节目。

Transport Stream
由ISO/IEC Standard 13818-1定义的一种容器格式，设计用于音、视频的复接和同步输出。TS提供在不可靠介质（网络）上传输数据的故障恢复能力，被广泛用于广播电视系统中，如DVB和ATSC。

Program Stream
由ISO/IEC Standard 13818-1定义的一种容器格式，一般被用于可靠介质上（如 DVD光盘）的数据传输。

http://www.vbrick.net/的一篇文章把Transport Stream和Program Stream各自的特点以及适用的场合等问题讲得颇为生动，我把它贴过来（有所修改，去掉了广告:)）。

We are talking about how MPEG-2 is delivered, NOT how it is encoded.  So whether a video is Transport Stream or Program Stream has nothing to do with the quality of the video encoding or the MPEG-2 GOP structure.   In other words, a beautiful woman can arrive at a party via a car, truck, or bus and she would still be a beautiful woman.  So the format for delivery is independent of the content.

Why are there two formats?  Well, because there are conflicting applications.  If you want to save MPEG-2 to a file on your computer, you are not very concerned about transmission.  If you want to transmit MPEG-2, you are not very concerned with file format.  Happily, the MPEG-2 standards address both.

Unfortunately, we have some trouble with language.  The word "Program" could mean "what I'm watching on TV", or it could mean "a channel", or it could mean "a specific format".  We are talking about the format, and to avoid confusion, I'll try to use the word "content" when talking about the MPEG-2 audio/video.  But you need to be aware that different industries use the term "Program" in different ways!

It is very important to point out that "Program Stream" has a very specific meaning. MPEG-2 has two different multiplexing schemes: Program Stream and Transport Stream.  The Program Streams are mostly used in storage applications.  Broadcast usage commonly uses the Transport Stream format.  If you have  one content channel (one program), it does NOT imply that the stream that carries the program would be a Program Stream.  In broadcast usage it would be a so-called Single Program Transport Stream (as defined by ISO 13818-1): a multiplexed collection of concatenated Program Streams without beginning or end. 

 

• An MPEG-2 Program Stream contains one, and only one, content channel.  A Program Stream is like a single-passenger car without shock absorbers: drive it on a smooth road.
• An MPEG-2 Transport Stream can contain one or more content channels. A Transport Stream is like a high end car or bus: it can carry one or more passengers and has a good suspension system that can handle the bumps in the road. 
• Authoring tools, such as Adobe, Avid, ULead, Media100, can produce MPEG-2 Program Streams (usually with 3rd party plug-ins).  This is because the intended applications are the creation of files for distribution on disk, including DVD.  Some vendors like to stream Program Streams directly...but this is not a good solution because it is not compliant with the broadcast industry, Set Top Boxes, and is error prone.
• In the DVB (satellite TV) world, a satellite needs to deliver, via radio, one stream to subscribers.  That one stream needs to carry many TV channels.  To do this, the many channels are multiplexed into a Transport Stream.  The receiver actually receives all of the channels at once (it has no choice!), but it only demultiplexes and then decodes the selected content, one at a time, from the delivered Transport Stream.
• When sending MPEG over IP, there is less value in having one Transport Stream that contains multiple content channels.  It is more useful, flexible, and uses less bandwidth when each content channel has its own IP multicast address.  
• Commercial broadcasters and cable companies use Transport Stream format for delivery of content to Set Top Boxes.  In a mixed, streaming-to-the-desktop,  and STB world, it is better to use only one format which takes you to Transport Stream.

 

So, which is "better", Transport Stream or Program Stream?  The answer is Transport Stream if you are talking about streaming, and Program if you are talking about authoring.