An Analyser is a software component used to scan the Hardware of Slaves and NPCs. The accuracy of of an analyser is dependant on your CPU, as a higher quality CPU will give more accurate results than lower quality CPUs. Analyser files range from 0.1 to 5, with 5 being the most useful.
Using an analyser requires that the .ana file is uploaded to the target Slave or NPC and then run on that system. Once run, you will be able to see the hardware statistics of the Slave or NPC in your Slaves menu.