library titering and amplification - (Jul/01/2006 )

Can someone please explaining to me briefly what does titering and amplification of a cDNA library mean? When we buy a cDNA libarry is not ready to use?
Thanks

TITERING MEANS THE DETERMINATION OF the ratio of THE NEMBER OF RECOMBINANT CLONES (phage) .
the cDNA library must be constructed not to bye.
send me more information about your work