Aleph is the first letter of the Hebrew alphabet and it is silent.
Like all of the Hebrew letters, its name comes from a word in Hebrew, or in one of the languages closely related to Hebrew, and it was originally a pictogram. The name of Aleph comes from the word for 'ox' or 'herd', and it was a picture of the head of an animal. There are related words in Hebrew that mean 'a thousand' [elef], 'champion or general' [aluf], and 'training or taming' [illuf]. The word [ulpan] meaning a place of instruction, or a Hebrew language academy, also comes from this root.
Now let's learn the vowels. Modern Israeli Hebrew pronunciation only distinguishes five vowel sounds - [a, e, i, o, u], like in Spanish - but classical Hebrew grammar drew distinctions between long and short vowels, and these are preserved in writing. (The Composite Shva is something we'll learn later when we study grammar.)
Each vowel is written below its accompanying consonant, and is pronounced after it. (There’s an exception to this, which we’ll learn later.) When you read pointed Hebrew - that is, Hebrew written with the vowels - your eye basically follows a sawtooth pattern, going from letter to vowel to letter to vowel.
Also you should know that one of the distinctive features of the Ashkenazi (European) dialect is that the vowel Kamats [אָ] is pronounced roughly like a short O or "aw" sound in certain positions. This explains why you might sometimes see a word like [shalom] written in English letters as [sholom]. And some Ashkenazi speakers pronounce the long O [אוֹ] almost like 'oy'. Oy!
Remember that the vowel marks are not considered part of the Hebrew alphabet proper - although there are certain letters of the alphabet that sometimes function as vowels. We'll learn more about these shortly. (As a side note, the Yiddish language - the Germanic folk language of the Ashkenazi Jews - works differently. But we're learning Hebrew here.)
The most important thing to remember is that the vowel marks are an aid to pronunciation - training wheels, if you like - and most everyday Hebrew is written without them.
ETA: Another look at the vowels.
|אָ||ah 'father' (Kamatz)||Ashkenazi speakers pronounce this like 'o' or 'aw' in some words.|
|אֵ||ey 'they' (Tsere)|
|אִי||ee 'feel' (Chirek)|
|אוֹ||o 'go' (Cholam)||Some Ashkenazi speakers pronounce this almost like 'oy'.|
|אוּ||oo 'fool' (Shuruk)|
|אַ||ah 'father' (Patach)|
|אֶ||eh 'pet' (Segol)|
|אִ||i 'pit' (Chirek)|
|אֹ||o 'for' (Cholam)|
|אֻ||u 'put' (Kubutz)|
In addition, there is the silent vowel [אְ] (Sheva) which may be pronounced as a neutral sound ('uh') or not at all.