What is the difference between digital printing and conventional printing?

That is not neccearily true. There are some digital presses that use actual ink. The Heidelberg QM, and the HP Indigo.

The difference between digital printing and conventional printing is

Digital printing is printed with CMYK toners, offset printing uses regular ink, not toners. I found information about this when i was inquiring about printing for my school for the coming year and did lots of research which guided me to http://www.superfineprinting.com/ Good luck on all your printing!