The crude is analysed in a laboratory in order to determine what chemical molecules is consistes of. The ligther components C1-C6 are usually reported directly. The the laboratury will do a destillation and report a number of cuts, their boiling points and average molecular weight.
Other parameters and tests will also be performed.
The engineer then uses specialists software (e.g. PVTsim) so characterise the fludi - that is to etablish a fluid with a number of pseudo components that exhibits the same properties as found in the tests nentined above.
The pseudocomponents are usually with a molecular weight higher than that of hexane (C6). Usually 3-12 pseducomponents are generated.
The significance? Idont really understand this question but if you dont characterize then you cant do any further process simulations. Once you get above C5 an enromeus number of molecules with the same number of carbon atoms exists and a complete chemical breakdown would be very impractical.
Best regards
Morten
