Yhyjyk

I have read the following in the x86 Wikipedia page:

The term "x86" came into being because the names of several successors
to Intel's 8086 processor end in "86", including the 80186, 80286,
80386 and 80486 processors.

But what does the "x" in "x86" represent? Is it a "variable" that can be something like "801" or "286" or "803" or "804"?

The term x86 is shorthand for 80x86, which was used to refer to any member of the family 8086 (and also, incidently, 8088), 80186, 80286, etc. Things have since gotten a bit muddled by the fact that while an 80386 had a mode that was compatible with the old architecture, it also introduced a fundamentally new mode which was shared by the 80486 as well as "named" processors like the Pentium, Pentium Pro, etc., and thus it is sometimes ambiguous whether the name "x86" is used in reference to the architecture that started with the 8086, or the one which had its debut with the 80386.

In modern usage it also means software which only uses the 32-bit architecture of the earlier 80x86 processors, to distinguish it from 64-bit applications.

Microsoft uses it that way on 64-bit versions of Windows, which have two separate directories called "Program Files" and "Program Files (x86)."

The 32-bit applications will run on 64-bit hardware, but the OS needs to provide the appropriate 32 or 64 bit interface at run-time.

It just means any processor compatible with same architecture.
So it includes 8088, 8086, 80186, 80286, 80386, 80486, Pentium, etc..

x is meant as wildcard, so this represents all CPUs able to run 8086 compatible code.