Added help text for the channel header and purpose dialogs

web/react/components/edit_channel_purpose_modal.jsx

@@ -69,6 +69,11 @@ export default class EditChannelPurposeModal extends React.Component {
             title = <span>{'Edit Purpose for '}<span className='name'>{this.props.channel.display_name}</span></span>;
         }
 
+        let channelTerm = 'Channel';
+        if (this.props.channel.channelType === 'P') {
+            channelTerm = 'Group';
+        }
+
         return (
             <Modal
                 className='modal-edit-channel-purpose'
@@ -81,6 +86,7 @@ export default class EditChannelPurposeModal extends React.Component {
                     </Modal.Title>
                 </Modal.Header>
                 <Modal.Body>
+                    <p>{`Describe how this ${channelTerm} should be used.`}</p>
                     <textarea
                         ref='purpose'
                         className='form-control no-resize'