Is there any difference in the principle of position:fixed between mobile and PC?

I saw this passage on the Internet:
  fixedviewport
  fixed
  iOSfixedfixed
  
  <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=no"/>

it"s quite clear to see the above sentences, but why did you solve it by adding the following meta tag? I know that width=device-width sets the Layout viewport on the mobile to the width of the phone"s screen. The elements of the fixed are not still fixed relative to the entire page, and the sliding on the screen is just moving the so-called viewport?.

Apr.04,2021

according to the browser window, viewport tells the browser to use the ideal viewport so that the width of the layout viewport is the same as the width of the ideal viewport

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3ac4b-2c248.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3ac4b-2c248.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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