The markings in the Quran are called Tashkeel (تشكيل) which comes from the 3-letters SH - KA - LA. In urdu Shakal (insert Urdu) means face and similarly in Arabic means to ‘shape’ or ‘form’ something.
Tashkeel are 4: Fatha, Damma, Kasra, and Sukoon. The first three result in vowel movement (AA, OO, EE) called HARAKAT versus Sukoon is for ending the sound and not vibrating or extending it.
The word HARAKAT means movement whereas SUKOON means stillness or quiet: