The Roman Alphabet
Speakers of modern languages tend to pronounce Latin words using the rules for pronunciation for their own language. By studying how sounds change over time and examining ways other ancient languages with different alphabets wrote Latin words, scholars have deduced how Classical Latin (i.e., the Latin of Caesar's time) probably sounded.
The biggest difference between our alphabet and the Roman one is that, for the Romans, each letter represented only one sound, making Latin a truly phonetic language. Apart from that, there aren't many differences between the two. In fact, our alphabet is properly called the Roman alphabet! When the Romans borrowed it from their neighbors to the north, the Etruscans, they adapted it to suit the sound system of Latin. The Etruscans had done the same thing when they got it from the Greeks, who got it from the Phoenicians, who had adopted it from their neighbors, the Egyptians. Quite a pedigree!
What is “Church Latin”?
Church Latin is the Latin that has been used by the Roman Catholic Church for centuries. It's really just a later form of Latin whose pronunciation is more like Italian. The most notable difference comes with the letters g and c. When followed by the vowels e or i, g is soft (like in English “general”), and a c has a ch sound (as in “cheese”).
Table 2-1 The Roman Alphabet
You may have noticed a couple letters missing, namely j and w. J was added to distinguish between Latin's vowel i and the consonant ī. The letter w was added to do the same thing for Latin's consonant u.