It's use various from person to person. It is in fact a small computer which can fit in the palm of your hand. It has a operating system and a hardware and you can buy and use software for the PDAs. Finance professionals use it for investing, mortgage calculations, billing accounts, etc. Medical professionals use it for reference, patient data management and calculation purposes.
Every person find it useful in one or the other.
That's why they are gaining so much popularity. All rights reserved.