The active read-only property of the MediaStream interface returns a Boolean value that will return to be  true if the MediaStream is active, else false.
The MediaStreamTrackEvent interface represents events which indicate that a MediaStream has had tracks added to or removed from the stream through calls to Media Stream API methods. These events are sent to the stream when these changes occur.
The MediaStreamTrackEvent() constructor returns a newly created MediaStreamTrackEvent object, which represents an event announcing that a MediaStreamTrack has been added to or removed from a MediaStream.
The MediaStream interface represents a stream of media content. A stream consists of several tracks such as video or audio tracks. Each track is specified as an instance of MediaStreamTrack.
The MediaStream.addTrack() method adds a new track to the stream. The track is specified as a parameter of type MediaStreamTrack.
The MediaStream.onaddtrack property is an EventHandler which specifies a function to be called when the addtrack event occurs on a MediaStream instance. This happens when a new track of any kind is added to the media stream. This event is fired when the browser adds a track to the stream (such as when a RTCPeerConnection is renegotiated or a stream being captured using HTMLMediaElement.captureStream() gets a new set of tracks because the media element being captured loaded a new source.
The MediaStream.onremovetrack property is an EventHandler which specifies a function to be called when the removetrack event occurs on a MediaStream instance. This happens when a track of any kind is removed from the media stream. This event is fired when the browser removes a track from the stream (such as when a RTCPeerConnection is renegotiated or a stream being captured using HTMLMediaElement.captureStream() gets a new set of tracks because the media element being captured loaded a new source.
The MediaStreamTrack.onended event handler is used to specify a function which serves as an EventHandler to be called when the ended event occurs on the track. This event occurs when the track will no longer provide data to the stream for any reason, including the end of the media input being reached, the user revoking needed permissions, the source device being removed, or the remote peer ending a connection.
The Media Capture and Streams API, often called the Media Stream API or the Stream API,  is an API related to WebRTC which supports streams of audio or video data, the methods for working with them, the constraints associated with the type of data, the success and error callbacks when using the data asynchronously, and the events that are fired during the process.
The applyConstraints() method of the MediaStreamTrack interface applies a set of constraints to the track; these constraints let the Web site or app establish ideal values and acceptable ranges of values for the constrainable properties of the track, such as frame rate, dimensions, echo cancelation, and so forth.
The clone() method of the MediaStreamTrack interface creates a duplicate of the MediaStreamTrack. This new MediaStreamTrack object is identical except for its unique id.
The getCapabilities() method of the MediaStreamTrack interface returns a MediaTrackCapabilities object which specifies the values or range of values which each constrianable property, based upon the platform and user agent.
The getConstraints() method of the MediaStreamTrack interface returns a MediaTrackConstraints object containing the set of constraints most recently established for the track using a prior call to applyConstraints(). These constraints indicate values and ranges of values that the Web site or application has specified are acceptable for the included constrainable properties.
The MediaTrackConstraints dictionary is used to describe a set of capabilities and the value or values each can take on. A constraints dictionary is passed into applyConstraints() to allow a script to establish a set of ideal values and/or preferred ranges of values for the track, and the most recently-requested set of custom constraints can be retrieved by calling getConstraints().
The MediaTrackSupportedConstraints dictionary establishes the list of constrainable properties recognized by the user agent or browser in its implementation of the MediaStreamTrack object. An object conforming to MediaTrackSupportedConstraints is returned by MediaDevices.getSupportedConstraints().
The MediaStreamTrack interface represents a single media track within a stream; typically, these are audio or video tracks, but other track types may exist as well.
The MediaTrackSettings dictionary is used to return the current values configured for each of a MediaStreamTrack's settings. These values will adhere as closely as possible to any constraints previously set using applyConstraints(), and will adhere to the default constraints for any properties whose constraints haven't been changed, or whose customized constraints couldn't be matched.