An angel investor is an individual who invests in start up companies for hope of a high return on their money. Instead of investing in the stock market or mutual funds, Angels take high risk investments with new companies.
So, yes, it's like a loan. Maybe you've heard of venture capitalists? They do the same thing, but with higher dollar amounts ... usually $500k - millions.
Angels deal in smaller amounts requested by startups...typically under $250k.