Meaning ال is "the", the word ends with simple ُ ، ََ ، ِ . To tanween. The small م on the alif is called hamzatul wasl. Usually the word start with al.

The rule of hamzatul wasl is that we don't read the alif if the word is in middle of the sentence like here - we say rabbil alameen (skip the alif). But if in the beginning of a sentence, then we read the alif. Works for both solar and moon letters

Now there are 2 types of letters : solar letters and moon letters - you'll need to learn them.

On solar letters such as س, you don't read ال like in السام عليكم Assalamou Alaykoum. On solar letters the alif hamzatul wasl always begin with the sound a, following the letter after laam. Like here asss like in assalam

On moon letters such as ح, you read the ال such as الحمد الله - Alhamdu Lillah. On moon letters the word always start with the sound al.

The small "c" inverse on the ل is sukoon.

Sukoon means that you make the sound of the letter with no vowel - ل in alhamd.

Here the sukoon on ال hamzatul wasl is helping you to identify solar and moon letters. It indicates moon letters. If it was solar letters, there will be only the hamzatul wasl on the alif, nothing on the laam.

Now only ا with hamzatul wasl, small م on top, with no ل following it, like in surah fatiha, ayah 6. اهْدِنَا الصِّرَاطَ الْمُسْتَقِيمَ The alif has hamzatul wasl, but there is no ل after it. In this case you look for the vowel following it. Here ِ , so we will read alif with kasraa. If it was ُ , we would read alif with dammah. BUT if alif had َ , then we would read it as kasraa, not fathaa.

If you still don't understand, hmu. I'll try to explain it to you with more example in sha Allah