VSWR (Voltage Standing Wave Ratio) is a measured value of how efficiently RF power is transmitted and is expressed as a ratio of the maximum to minimum amplitude (voltage or current) of the corresponding field component appearing on a line that feeds an load.
Loss in % is the percentage of power that is lost to the load and returns back to the system as a reflection. A high % loss means more power is lost at the load.
Return loss is the amount of power that is lost in the load and returns back to the system as a reflection typically expressed in dB. A high return loss means more power is lost at the load.
Reflection Coefficient the amount of the electromagnetic wave that is reflected by an impedance discontinuity in the transmission line (medium). It is a ratio of the amplitude of the reflected wave to the wave incident at the junction.
Mismatch loss is a measurement describing the amount of power that will not be available at the load due to the reflected wave. It indicates the amount of power lost in the system due to the mismatched impedances.