Operational Taxonomic Unit (OTU) - what is it? (Dec/26/2009 )

Dear all,

I have searched the web and I found some websites that speak about this and give some sort of definition, but its hard for me to really grasp the idea behind this or what it really means.
Maybe someone here can explain it to me so that I understand it more?

thanks

As far as I remember OTUs are just a kind of wild-card/placeholder for any taxonomical unit (e.g. species, population, strains, and any other biological groups) someone works with or someone wants to explain something more general (without the need to define this) in relation to phylogenetics and population genetics.