I understand this is very old post. However, I thought I would share my understanding if you are still interested to know.
The data records are read into the memory, so that all the processing of data may be done through memory. I am sure you know this bit. QlikView treats all the data as Data Element Type (Columns / Fields) and Data Element Values (Values / Records). So each different data element value of each data element type is assigned a binary code and the data records are stored in binary-coded form and they are also sorted. By using the binary coding, very quick searches can be done on the tables. Also, QlikView removes the redundant information information and reduces the amount of data. However, the redundant information in stored as seperately with the frequencies for each unique data element value and across each data element type. When user makes a selection on data element values then the implied selection (possible values) are kept track seperately to present them to the user. By this process QlikView can perform rapid linear searches.
I understand this is not in detail but just a quick overview. I hope this helps!
Cheers - DV