a DOCX file is a Microsoft Word document that typically contains text.

DOCX is the newer version of DOC, the original official Microsoft Word file format. 

JavaScript Object Notation (JSON) is a standard text-based format for representing structured data based on JavaScript object syntax.

It is commonly used for transmitting data in web applications (e.g., sending some data from the server to the client, so it can be displayed on a web page, or vice versa)

A DFXP file is a file format used to add captions to video content. DFXP is short for “Distribution Format Exchange Profile” and is a standard file type for XML captions.

This type of captioning format will feature a .dfxp extension and is compatible with many major media hosting platforms, as well as applications like Adobe Flash and Microsoft Silverlight.

WebVTT format for HTML5 video.

The syntax for the align: tag is A:middle.

Contains information for displaying timed text tracks (such as subtitles or captions) using the Web Video Text Tracks (WebVTT) format. The timed text tracks includes information such as subtitles or captions.

The purpose of VTT file is to add text overlays to a <video>.

The format is somewhat similar to the SRT files. WebVTT based text files are encoded using UTF-8. A VTT file contains information such as subtitles, descriptions, captions, descriptions, chapters, and metadata.

Being plain text files, VTT files can be opened using text editors such as Microsoft Notepad, Apple TextEdit, and Notepad++.

Captions for YouTube, older JW FLV Player or for DVD subtitles longer than 32 characters per line.

It's a simple subtitle file saved in the SubRip file format with the .srt extension.

It contains a sequential number of subtitles, start and end timestamps, and subtitle text.

SRT files make it possible to add subtitles to video content after it is produced.

SAMI files are text files that have an .smi or .sami file name extension.

They contain the text strings used for synchronized closed captions, subtitles, and audio descriptions.

They also specify the timing parameters used by the Windows Media Player control to synchronize closed caption text with audio or video content.

When a Windows Media file reaches a time designated in the SAMI file, the text changes accordingly in the closed caption display area of the Web page

SAMI captions for Windows Media video or audio (.WMV, .WMA, .ASF, .MP3, .WAV, …). Also used for Camtasia and other systems.

Text files that have an . smi or . sami file name extension.

They contain the text strings used for synchronized closed captions, subtitles, and audio descriptions

DFXP timed text for Flash with begin/end tags.

See .ADB.XML above for DFXP timed text with dur syntax. Compliant with the TTML specifications.

A standard file type for XML captions. This type of captioning format will feature a . dfxp extension and is compatible with many major media hosting platforms,
as well as applications like Adobe Flash and Microsoft Silverlight

The SMPTE-TT file is the FCC standard for internet captioning.

It's derived from the DFXP format, but contains some extra fields to support the broadcast industry.

It is also sometimes called TTML, SMPTE-TTML, or SMPTE-2052.

This format supports a "708" style captions, being suitable for broadcasters looking for 708 captions or HD captions.

It also supports vertical and horizontal positioning, so it is suitable for all FCC requirements.

There is an increasing number of applications accepting the SMPTE-TT format, like Adobe Premiere.