doc: clarify Readable paused/flowing!==object mode

- Clarify that a `Readable` stream's reading mode (paused vs. flowing)
  is independent of its object mode (object vs. non-object).  I am
  relatively new to Node streams, and was briefly confused while
  reading the docs by the two uses of the word "mode".

- Copyediting: add missing apostrophes; minor grammatical changes

PR-URL: #22619
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Denys Otrishko <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>

doc/api/stream.md

@@ -70,7 +70,7 @@ buffer that can be retrieved using `writable.writableBuffer` or
 `readable.readableBuffer`, respectively.
 
 The amount of data potentially buffered depends on the `highWaterMark` option
-passed into the streams constructor. For normal streams, the `highWaterMark`
+passed into the stream's constructor. For normal streams, the `highWaterMark`
 option specifies a [total number of bytes][hwm-gotcha]. For streams operating
 in object mode, the `highWaterMark` specifies a total number of objects.
 
@@ -576,15 +576,18 @@ Examples of `Readable` streams include:
 All [`Readable`][] streams implement the interface defined by the
 `stream.Readable` class.
 
-#### Two Modes
+#### Two Reading Modes
 
-`Readable` streams effectively operate in one of two modes: flowing and paused.
+`Readable` streams effectively operate in one of two modes: flowing and
+paused. These modes are separate from [object mode][object-mode].
+A [`Readable`][] stream can be in object mode or not, regardless of whether
+it is in flowing mode or paused mode.
 
-When in flowing mode, data is read from the underlying system automatically
+* In flowing mode, data is read from the underlying system automatically
 and provided to an application as quickly as possible using events via the
 [`EventEmitter`][] interface.
 
-In paused mode, the [`stream.read()`][stream-read] method must be called
+* In paused mode, the [`stream.read()`][stream-read] method must be called
 explicitly to read chunks of data from the stream.
 
 All [`Readable`][] streams begin in paused mode but can be switched to flowing
@@ -633,22 +636,22 @@ within the `Readable` stream implementation.
 Specifically, at any given point in time, every `Readable` is in one of three
 possible states:
 
-* `readable.readableFlowing = null`
-* `readable.readableFlowing = false`
-* `readable.readableFlowing = true`
+* `readable.readableFlowing === null`
+* `readable.readableFlowing === false`
+* `readable.readableFlowing === true`
 
 When `readable.readableFlowing` is `null`, no mechanism for consuming the
-streams data is provided so the stream will not generate its data. While in this
-state, attaching a listener for the `'data'` event, calling the
+stream's data is provided. Therefore, the stream will not generate data.
+While in this state, attaching a listener for the `'data'` event, calling the
 `readable.pipe()` method, or calling the `readable.resume()` method will switch
-`readable.readableFlowing` to `true`, causing the `Readable` to begin
-actively emitting events as data is generated.
+`readable.readableFlowing` to `true`, causing the `Readable` to begin actively
+emitting events as data is generated.
 
 Calling `readable.pause()`, `readable.unpipe()`, or receiving backpressure
 will cause the `readable.readableFlowing` to be set as `false`,
 temporarily halting the flowing of events but *not* halting the generation of
 data. While in this state, attaching a listener for the `'data'` event
-would not cause `readable.readableFlowing` to switch to `true`.
+will not switch `readable.readableFlowing` to `true`.
 
 ```js
 const { PassThrough, Writable } = require('stream');
@@ -660,20 +663,20 @@ pass.unpipe(writable);
 // readableFlowing is now false
 
 pass.on('data', (chunk) => { console.log(chunk.toString()); });
-pass.write('ok'); // will not emit 'data'
-pass.resume(); // must be called to make 'data' being emitted
+pass.write('ok');  // will not emit 'data'
+pass.resume();     // must be called to make stream emit 'data'
 ```
 
 While `readable.readableFlowing` is `false`, data may be accumulating
-within the streams internal buffer.
+within the stream's internal buffer.
 
-#### Choose One
+#### Choose One API Style
 
 The `Readable` stream API evolved across multiple Node.js versions and provides
 multiple methods of consuming stream data. In general, developers should choose
 *one* of the methods of consuming data and *should never* use multiple methods
 to consume data from a single stream. Specifically, using a combination
-of `on('data')`, `on('readable')`, `pipe()` or async iterators could
+of `on('data')`, `on('readable')`, `pipe()`, or async iterators could
 lead to unintuitive behavior.
 
 Use of the `readable.pipe()` method is recommended for most users as it has been
@@ -832,7 +835,7 @@ In general, the `readable.pipe()` and `'data'` event mechanisms are easier to
 understand than the `'readable'` event. However, handling `'readable'` might
 result in increased throughput.
 
-If both `'readable'` and [`'data'`][]  are used at the same time, `'readable'`
+If both `'readable'` and [`'data'`][] are used at the same time, `'readable'`
 takes precedence in controlling the flow, i.e. `'data'` will be emitted
 only when [`stream.read()`][stream-read] is called. The
 `readableFlowing` property would become `false`.
@@ -2478,3 +2481,4 @@ contain multi-byte characters.
 [readable-destroy]: #stream_readable_destroy_error
 [writable-_destroy]: #stream_writable_destroy_err_callback
 [writable-destroy]: #stream_writable_destroy_error
+[object-mode]: #stream_object_mode