Legion

In short: Aliasing is the way an x86 CPU maps an assembler address to a physical address.

You may have seen stuff like segment:offset in regard to addressing. For a real location this could be 0000:7C00. This means: Segment 0000, offset 7C00, and this is where your computer starts when it boots.
But this is not an absolute address. The segment is shifted four bits to the left and added to the offset. So the absolute address for 0000:7C00 is 07C00. Now, consider this address 07C0:0000. So segment 07C0 and offset zero. You shift the segment four to the left making 7C00 and then add the offset of zero. The result is 7C00 which is the same as 07C00.
Result: 0000:7C00 is the same physical address as 07C0:0000.
You will see this throughout articles you find on the subject, and they will mix these up. Learn to read these as their proper physical addresses.
You will need this when your code bugs out, because your code may execute at segment 0000 and your data may be read/written at segment 07C0. Effectively making your code work some times and bug out at other times. If in doubt, make sure you're at the correct segment. This because most assembler instructions will not update the segment, but assume it's correct. So if the segment is set to 07C0 and you try to read offset 7C58, you will get a weird result. 07C0:7C58 (07C0 « 4 + 7C58 = 08418) is obviously not the same as 0000:7C58 (07C58).

Just be aware of this functionality of the x86 processor when things does not work as you thought it would.