How USB is different from RS-232

[alexxx]

Other things like handshaking u mean ?

USB doesn't only specify things like speed and low level interfacing as RS232, but a lot of other things. RS232 lacks higher level specification like frames format. You can just send raw bytes.
Reading the USB 1 specification for instance, someone can see terms like bus topology, USB host & devices, bus protocol, error detection and handling, removal of USB devices and more. Handshaking is also one of them.
http://esd.cs.ucr.edu/webres/usb11.pdf

You can download specification versions from here:
http://www.usb.org/developers/docs/

 

[D.A.(Tony)Stewart]

I had a typo read #9 again then #18

 

[tpetar]

The difference between RS-232 and USB is that RS-232 is hobbyist-friendly and USB is not.

Yes UART have many uC and its easy to use, but if you look some uC with builtin USB support, you realize that USB not so hard to use. Also usage of FT232 and such chips for converting USB to UART is not hard.

 

[D.A.(Tony)Stewart]

Most people think of only the Physical differences, but there are many more than this.

The differences are more than what's in common for USB and RS-232. YOu might have just as much in common with a Mouse port PS-2 or IRDA. But to emulate USB would require a host with custom software to recognize non-defacto devices with drivers. i.e. very custom.
But you need to read the books, not enough room here. Start with the 7 layers of communication in the OSI standard and note all the differences in every layer, then report back.

Added:
Although the OSI protocol was proposed with the OSI model, it was never adopted and the TCP/IP emerged instead to satisfy the same open std requirements.