Harakaat (singular Harakah) are vowel signs on Arabic letters that help in pronunciation. In printed or hand-written text, you may or may not see any harakaat present. If harakaat are not present, they are implied. A native speaker knows how to pronounce them.
But for printed copy of Quran, in children’s book or in books for learners, the words mostly have harakat.
Text with harakat -
ٱلْحَمْدُ لِلَّهِ
Text without harakat -
الحمد لله
There are many types of harakaat. We will only have most important ones that are relevent for
learning Arabic grammar.
Most important harakaat are:
Fatah (فَتْحَة)
This looks like a line on top of the letter. e.g. حَ in - ٱلْحَمْدُ لِلَّهِ This give a sound 'a'.
So a حَ is pronounced a 'Ha' in the phrase Alhamdu lillah.
Dammah (ضَمَّة)
This looks like a comma sign on top of a letter.
e.g. دُ in - ٱلْحَمْدُ لِلَّهِ This gives a sound 'u'
Here دُ is pronounced as 'du' in the phrase Alhamdu lillah.
Kashrah (كَسْرَة)
This looks like a slanted line at the bottom of a letter.
e.g. لِ in - ٱلْحَمْدُ لِلَّهِ So لِ is pronounced as 'li' in the phrase Alhamdu lillah.
Sukun (سُكُون)
This looks like a round circle or a angle sign on top of a letter.
e.g. - مْ in - ٱلْحَمْدُ لِلَّهِ Sukun is rather absence of a vowel. It creates a suddend stop in pronunciation.
So مْ is pronounced as 'm' in the phrase Alhamdu lillah.
Also important are:
Tanween (تَنْوِين)
Tanween is a doubling of a vowel sign, like double fatha or double dammah or double kasrah.
They are pronounced with -an, -un, -in
Examples:
كِتَابً - kitaban
كِتَابٌ - kitabun
كِتَابٍ - kitabin
Shaddah (شَدَّة)
This is doubling of a letter in a word. This is indicated by a 'w' like sign.
Examples:
عَلَّمَ - 'allama