is that true iphone camera is good enough to take photos?

[deep blue2]

A cameraphone will take reasonable pictures in good light - so it's ok for those conditions. The images Mark linkied to are all taken outdoors on a very sunny day, so no issues.

The limitations outweigh the pros though;
- the depth of field will always be very deep because of the lens
- you won't have the ability to produce large prints because of the small sensor size
- in poor illumination or at night the cameraphone will struggle, producing noisy poor qualtiy images
- you have little or no control over exposure parameters, (you won't be able to change settings) so if your goal was to learn about the technical side of photography, forget it.

The cost of a second hand DSLR on eBay will be way less than an iPhone - you're better off with that if you want to be a 'real' photographer.