What is an Account?
Account is a level higher than property within an organization and is essentially your access point for Google Analytics. One organization can have more than one GA accounts, but in order to gain access to GA and choose the properties you wish to keep track of, you need to have at least one account within GA.
The nature of the account-property relationship can be either one-to-one (one account to one property), or one-to-many (one account to many properties).
What is a Property?
Property is usually a webpage, a mobile app, or a device. More than one property can be owned by one account.
Your GA account lets you add various properties that you can glean useful data from. GA does this via a tracking code that carries a unique ID, so it will be easily identifiable and shown within your reports.