Emulsification happens in cooking when fat droplets are broken down and able to be suspended in water.  In the case of this salad dressing, the oil and lemon juice, along with the honey, mustard and seasoning, are blended at a high speed allowing the oil to break apart into small droplets that are dispersed and suspended in the lemon juice.  You’ll know it has emulsified because it will turn from watery looking to creamy looking.  If an emulsification breaks, you can generally bring it back by blending or shaking very well.