Question about SDRAM

i don't understand some definitions about SDRAM:

1)COLUMN: smallest unit data....if SDRAM is 4Mx16(=1megx16x4banks), is 16 colum's number of bits or data out bits?Column's number of bits and data out pins are always the same or can differ each other? 2)BANK: in datasheet i found 1,2,4,etc...are these bytes or cells? For example, if bank=2, i obtain 2*16=32bit or 2*8=16bit? Thanks