Partitioning the SD card!
Actually, partitioning gives you the benefit of using space in your SD Card to install apps or use app data, instead of cramming it all up in the phones' internal memory. In other words, the Second Partition acts as the internal memory of the phone. So creating a 1 GB partition for a device with low internal memory allows the user to install more apps and doesn't let the internal memory decrease.
Link2SD can only accept partition with the proper scripts, i.e if the SD card has been partitioned with Ext2 then Link2SD must also be given the command for creating scripts as Ext2.
It is usually recommended to partition SD as Ext2 or Ext3 and create scripts on Link2SD as the same.
Hope it helped