copa structure

I know following are main tables in COPA structure

CE1xxxx actual line item

CE2xxxx plan line item

C3xxxx value fields (key figures)

CE4xxxx Characteristics table (similar to diemnsion table)

if i m not worng CE3xxxx will put into fact table of cube

and CE3xxxx will put into Dimension Table

<b>i m unable to understand CE1xxxx and CE2xxxx

where we use them.</b>

i will thank you by assinging points.