i.e.: 'In essence' or 'in other words'. It is used to clarify the original phrase with something specific. Edit: The Latin translation of i.e. is "that is to say" but the words I listed are what helps me remember.
It was sad to have reached the end, i.e., the final episode in the series.
'The end' and 'the final episode' are the same thing.
e.g.: 'For example'. Clarify the original phrase with an example.
He likes fruits, e.g., apples and oranges.
'apples and oranges' are examples of fruits he likes. There may be others.
viz.: 'Namely' or 'as follows'. Similar to e.g., it lists examples, but it is normally used when there is a definitive, complete list. Edit: As @Daniel Roseman says in the comment below, this is rarely used today.
He likes some fruits, viz., apples and oranges.
'apples and oranges' are the only fruits he likes.
So in your specific example of mobile device manufacturers, #1 is probably most likely but it would depend on the sentence:
AT&T offers phones from several mobile device manufacturers e.g. Nokia and Samsung. AT&T offers other phones, too.
Bob's Phone Shack sells mobile phones from Bob's favorite mobile device manufacturers, viz. Nokia and Samsung. Bob only sells Nokia and Samsung phones.
The Oatmeal (very funny)