An absolute is a highly concentrated aromatic extract made through solvent extraction (typically hexane) followed by an alcohol wash, a method used for delicate flowers like jasmine or rose that don't yield well through steam distillation. It tends to be thicker, darker, and closer to the plant's true scent than an essential oil.
All of the products I have purchased from Original Swiss Aromatics are excellent. I buy from them because their standards are high. Their Indian frankincense is one of the most important oils to own.