請問買機票時, L , V, Q, W...CLASS 等等, 代表甚麼呢?

They represent the sub-class in each First/Business/Economy class...
Different sub-class have different price/condition/restriction...
Usually the lower the class (Cheaper ticket), there would be more restriction like Monday-Thursday only (As Friday to Sunday demand is higher), no change of date/time, no refund if cancellation, shorter maximum staying time etc... And as the ticket is more expensive, there will be less restriction/condition...
Like if you get a Full fare Economy class ticket which is Y class, your ticket will have more or less no restriction on changing date/time... But 1 restriction is that it will be within 1 year...

all Economy Class but different fares and conditions.

they represent different conditions on pricing, routing, restrictions etc. different airlines have different classification.

是座位的分類, 不同分類, 價錢可以不同, 限制亦有所不同.