Why are the following debits and credits?

Balance sheet equation:
DR = CR
Assets = Liabilities + Equity

When you think of profit and loss/income statement/whatever it's called now:
Revenue - Expenses = Profit
Profit can be retained, and will end up as equity; so positive revenue and profit should be CR under equity
DR = CR
Expenses = Revenue, Profit (Balance b/f)

Sales sold on credit is an asset because it has economic benefits, but it's not yet turned into cash. Sales account goes up because of revenue; VAT is a liability, but also makes up the sales figure.
When VAT is expensed, it will be debited to reduce the balance on the VAT liability account.
The sales is registered as an outstanding balance for the company to collect i.e. in debtors account/trade receivables

Hope that helps

The book I'm sticking from (Osborne Tutorial for Bookkeeping Transactions) has the equation as capital instead of equity, am I to assume they're interchangeable or is this something different?