The Armenian alphabet was created in the 5th century CE by Saint Mesrop under influences from Greek (as reflected in the alphabetical order and the left-to-right direction of writing). The alphabet's original 36 letters were well suited for the Old Armenian language. Two additional letters, "o" and "fe", were added later during the late Middle Ages to write loan words, bringing the total number of letters to 38.
The Old Armenian language was the only written form of the language from the 5th to the 19th century, while in the intervening centuries, phonological changes have split the Armenian language into two dialects, namely Eastern and Western. However, only the Eastern dialect is taught as the written form at school nowadays as it is closer to the historical Old Armenian form, even though the Western dialect is more widely spoken.
In the following chart, both the Eastern (EA) and Western (WA) phonetic values for each letter are given. The name of the letters are given in the Eastern dialect, but you can directly translate any name to its Western version by simply mapping all the Eastern phonetic values to their Western counterparts.