XIRR is a financial function in Google Sheets that calculates the internal rate of return for a series of cash flows occurring at irregular intervals.

The XIRR function takes in two arrays of arguments:

"cashflowamounts" which represents the cash flows, including the initial investment as a negative value, followed by all subsequent cash flows as positive values. "cashflowdates" which represents the dates of each cash flow. Optionally, you can provide a third argument, "rate_guess", which is an estimate for the expected internal rate of return.

The XIRR function returns the internal rate of return (IRR) for the series of cash flows, which is the interest rate at which the net present value of all cash flows equals zero.