What is offset in hexadecimal?

An offset is an index into something. When using hex it typically deals with offsets into memory or files to find key data.

For example, a index table in a file may start at offset 100h or 256 decimal.

If you look at http://en.wikipedia.org/wiki/JPEG it gives you a table of segments and their lengths in hex. You use that value to find the offset to the next segment definition in the file.

I'm not sure if that gives you what you want since the question is not exactly clear.

I'm not sure I understand the specific question you're asking. 'offset' gets used in a few different ways when you're dealing with hex code; usually it's a way of referring to a specific set of numbers within a larger set of numbers. thus, the hex for the character 'a' in unicode is 0x0056, and sometimes people might refer to the second byte (56) as an offset. or sometimes if you have a subroutine listed in machine code people will talk about a certain command in terms of its offset from the beginning of the code block.