What is the difference between a monostatic and a bistatic radar configuration?

Monostatic radar: the transmitter and receiver are co-located (same antenna or closely spaced antennas). This is the standard radar configuration. Advantages: simple geometry (range determined by round-trip time), single platform, and well-understood signal processing. Bistatic radar: the transmitter and receiver are at separate locations, separated by a baseline distance. The target range is determined by the sum of the transmitter-to-target and target-to-receiver distances (an ellipse). Advantages: the receiver is passive (difficult to detect, jam, or attack), the bistatic RCS of the target may be larger than the monostatic RCS (especially in the forward-scatter region), and the system is resistant to anti-radiation missiles (which home on radar transmitters). Disadvantages: requires synchronization between TX and RX (timing and frequency), complex geometry (elliptical iso-range contours), and the bistatic radar equation includes both TX and RX antenna gains independently.