AE/BE abbreviation CMOS help

[prof. Antonio Guerrieri]

Hi all,

some CMOS ICs (for example the 4001) used in some synthesizer modules
contains an abbreviation such as AE , BE or B , UB which seems to suggest a
different purpose (may be buffered or unbuffered) for the ICs.
Could some one explain the difference, if any?
If such a difference exists, it is important or a type can be replaced from
the other type in a board ?
Could someone indicate exactly the corrispondence between the abbreviation
used and the type?

Thank.

Antonio