The problem E-Commerce Application solves

It can be a substitute for brick-and-mortar stores, though some businesses choose to maintain both.
Almost anything can be purchased through ecommerce today; for this reason, ecommerce is often highly competitive.
Ecommerce operates in several market segments including business-to-business, business-to-consumer, consumer-to-consumer, and consumer-to-business.

Challenges we ran into

Once that's determined, you need to come up with a name and set up a legal structure, such as a corporation.