In one sentence: CRM is an enterprise business strategy and eCRM is a powerful tool kit that helps implement the strategy.
Just as you cannot build a building without the plans, you can't implement a customer-centric business strategy without a design. Houses were once built from architectural blueprints using hand tools. When portable power tools became available, not only did buildings go up much faster but greater design opportunities opened up for architects.
Now, here's the rub: The power tools didn't design the buildings. Nor does eCRM--the use of electronic commerce and digital communication tools to help implement CRM--does design CRM strategies. eCRM is a spectacularly powerful implementation tool, but a tool nonetheless. And just as you don't use a circular saw to design a house, you don't use eCRM to design a CRM business strategy.