What are the segment and offset in real mode memory addressing?

Question

I am reading about memory addressing. I read about segment offset and then about descriptor offset. I know how to calculate the exact addresses in real mode. All this is OK,

Answer 1

I want to add an answer here just because I've been scouring the internet trying to understand this too. The other answers were leaving out a key piece of information that I did get from the link presented in one of the answers. However, I almost totally missed it. Reading through the linked page, I still wasn't understanding how this was working.

The problem I was probably having was from myself only really understanding how the Commodore 64 (6502 processor) laid out memory. It uses similar notation to address memory. It has 64k of total memory, and uses 8-bit values of PAGE:OFFSET to access memory. Each page is 256 bytes long (8-bit number) and the offset points to one of values in that page. Pages are spaced back-to-back in memory. So page 2 starts where page 1 ends. I was going into the 386 thinking the same style. This is not so.

Real mode is using a similar style even if it is different wording SEGMENT:OFFSET. A segment is 64k in size. However, the segments themselves are not laid out back-to-back like the Commodore was. They are spaced 16 bytes apart from each other. Offset still operates the same, indicating how many bytes from the page\segment start.

I hope this explanation helps anyone else who finds this question, it has helped me in writing it.