This is one of the best and most usefull software I have ever used. Truecaller gives me the details of those callers whos phone numbers are not saved in my smartphone. Whenever any unknown person call me truecaller show me the name and service provider of that unknown caller. Most of the time it gives me the right information and helped me many times.
I can also block any spam caller through this software. Apart from this I can also see facebook profiles of some callers through truecaller. Its very easy to use and understand just need to download it from any app store for free and registered your mobile number and thats it. Just I need to have internet connection to use this software although without internet its useless.