bootloader

Hello can someone please help me with the bootloader i read the links and all but they still didn't answer my question. can someone please tell me what does a bootloader do and i have the duimilanove ATMEGA328.
thank you for your help

The bootloader is a small program that runs on the chip when you reset the micro-controller. It can communicate with your computer and accept new code and store it in the chip's permanent memory. After that it starts the code. This typically happens when you press the upload button.

so is it possible for me to add a code from my sketch and click burn bootloader and if its possible how do i do that?
thank you for you help

If you’re asking this kind of question, you probably don’t want to be messing with the bootloader.
Can you explain waht it is you want to achieve?

just wanted to no if u could upload a skecth to the arduino using bootloader and thank you very much on helping me god bless

If you can upload a sketch normally, then surely you wouldn't want to upload it to a bootloader, even if it was possible?

Learn about fuses (not surge protection fuses though - the ATmega's internal fuses). It will give you a better understanding about bootloaders, what they do, and how they work. Also, it should be possible to 'permanantely' upload a sketch by using the fuses to prevent a different sketch from being uploaded. Using high voltage programming, you can reset the fuses, but not by simply clicking uplopad.
The bootloader stays on the Ic after you upload a new program, so it will stay on 'permanently*' if you use the correct fuses.

Onions.

*It will not be there permanently. Quoted from the ATmega328 datasheet, Data retention: 20 years at 85°C/100 years at 25°C.

thank you very much for your help