An extraction is a separation technique that makes use of differences in the distributions of solutes between two mutually insoluble phases. This technique is often used in sample preparation to remove analytes from interferences, to transfer analytes to alternative solvents, or to concentrate analytes prior to their analysis.
A liquid-liquid extraction is an extraction that is conducted with two immiscible liquids, one of which is the sample. The two phases used for the extraction are both liquids. After the analyte has distributed between the two liquids, these phases are allowed to separate. After these two liquids have formed distinct layers, the phase now containing the analyte is removed for later use or analysis.