1. Reliability Principle: This is the principle of reliable information which provides backup to every accountant. It is also called objectivity principle. An accountant is required check & rechecks their work in order to maintain the reliability. Reliability also helps in taking decisions and making predictions for the future.
2. The Cost or Historical Cost Principle: According to this principle an accountant has to record transactions based on actual costs without a markup in the value of assets & services.
3. The Matching Principle: Revenues and expenses should match the time period in which these are earned and incurred.
4. Full Disclosure Principle: According to this principle, necessary information like cost should be in an understandable format and presented in the main body of the financial statements with comments or notes, if necessary.

GAAP Concepts: These are also known as GAAP assumptions.

1. Periodicity: Information prepared and reported in a specific time period.
2. Going Concern: According to this concept, it is assumed that a business will be run for a long time.
3. Stable Monetary Unit: Results are recorded in monetary units i.e. dollar ($).
4. Economic Entity: All the profits and expenses of the business should be kept separate from personal expenses.

GAAP & Financial Statement: There are some forms that are used by an accountant to record a company's transactions:

1. General journal
2. Ledger
3. Trial Balance (I assume what was meant was Trial balance and not Trail balance)
4. Balance Sheet
5. Income Statement