title: Where is Children from mapStateToProps in redux official todo example?
body: <p>in <a href="https://redux.js.org/basics/exampletodolist#containers-filterlink-js" rel="nofollow noreferrer">https://redux.js.org/basics/exampletodolist#containers-filterlink-js</a>, the code of <strong>FilterLink.js</strong> is</p>
  
  <pre><code>import { connect } from 'react-redux'
  import { setVisibilityFilter } from '../actions'
  import Link from '../components/Link'
  ​
  const mapStateToProps = (state, ownProps) =&gt; ({
    active: ownProps.filter === state.visibilityFilter
  })
  ​
  const mapDispatchToProps = (dispatch, ownProps) =&gt; ({
    onClick: () =&gt; dispatch(setVisibilityFilter(ownProps.filter))
  })
  ​
  export default connect(
    mapStateToProps,
    mapDispatchToProps
  )(Link)
  </code></pre>
  
  <p>We can find obviously, <strong>active</strong> and <strong>onClick</strong> is passed to Link 
  component</p>
  
  <p>However, in Link component, <a href="https://redux.js.org/basics/exampletodolist#components-link-js" rel="nofollow noreferrer">https://redux.js.org/basics/exampletodolist#components-link-js</a>, the code is</p>
  
  <pre><code>import React from 'react'
  import PropTypes from 'prop-types'
  ​
  const Link = ({ active, children, onClick }) =&gt; (
    &lt;button
      onClick={onClick}
      disabled={active}
      style={{
        marginLeft: '4px'
      }}
    &gt;
      {children}
    &lt;/button&gt;
  )
  ​
  Link.propTypes = {
    active: PropTypes.bool.isRequired,
    children: PropTypes.node.isRequired,
    onClick: PropTypes.func.isRequired
  }
  ​
  export default Link
  </code></pre>
  
  <p>Where does <strong>children</strong> in <strong>Link</strong> props come from?</p>