PMCD
is the format that is known as the CD-R that you send after words to the replication or duplication

the PMCD is the whole album in 16 bit/44.1khz format

the reason its important to have the PMCD is that it has the edits,cuts,fades,gaps,crossfades,cd-text, ISRC codes, upc and all that info

sending the waves on the net can be sending each wave but that wont include the actual album flow - and thats very important
i strongly recommend having it done on a PMCD and sent to you

there are other formats that can be sent but you wont have the actual PMCD to check if you dont take it in that form

If you decide to make the flow of the album by yourself be aware that you will have to make the micro levels of the different songs --that is a big part of the mastering when the levels are made

so dont expect the songs to be at the same level when they are sent back as each song in correlation to the whole album

in most cases its the album sequencing that is where that process is made and the song levels are matched or controlled in a dynamic way

Stereo Interleaved " means one stereo track
not 2 mono tracks

WAV or AIFF
is just the files format and extention

you can send any bit resolution from 16 bit to 24 bit or even 32 bit floating point
sample rates from 44.1khz up 192 khz

i recommend asking
the mastering engineer what bit rate and sample rate he prefers getting

everyone likes to get the work different and can work different

its all about comunicating with him