In a standard lipid profile, lipid (fat globules called Total Cholesterol) are separated from the blood. The individual lipid particles are then identified and measured. These particles (called lipoproteins) are then given names according to how dense (heavy) they are. The particles of interest are High Density Liporotein (HDL), Low Density Lipoprotein (LDL), and Very Low Density Lipoprotein (VLDL) (sometimes called triglyceride).
This figure shows the various sizes of lipid particles that circulate around in the blood. Note that there are different sizes even for the same particle name and these sizes are often given a number or a letter designation.