GAAP (Generally Accepted Accounting Principles) - Vary by country but most people refer to US GAAP.
FASB (Financial Accounting Standards Board) - A Standard setting body that issues guidelines.
ASC 606 - Accounting Standards Codification related to revenue recognition.
Balance sheet - Has two sides - one reflects assets, the other liabilities & equity.
Income statement - Reflects the results of a period by showing revenue and expenses a company incurred.
Recognized Revenue - this is commonly only referred to as revenue and reflected in the income statement. Payments that fulfil the five criteria below can be considered recognized revenue.
Deferred Revenue - relates to payments that have been received by the company, but for which goods or services have not yet been provided. It is reflected as a liability on the balance sheet because the company is still liable to provide these goods or services.