Technical definition
A visual account with debits on the left and credits on the right.
How it works
T-accounts make postings and balances visible. Opening balance and transactions are placed on the appropriate side; the difference between both sides is the ending balance, normally shown on the account's normal-balance side.
Everyday example
Cash starts at 1,000 debit, receives 600 debit and pays 250 credit. Ending cash is a 1,350 debit balance.
Common pitfall
A T-account is a learning and analysis tool; it does not replace source documents or the formal ledger.