How xy different from x+y in "THE LAWS OF THOUGHT, ON WHICH ARE FOUNDED THE MATHEMATICAL THEORIES OF LOGIC AND PROBABILITIES" by Boole, George

Question

I was self studying https://archive.org/details/investigationofl00bool but could not go past the below sections. Chapter 2:6 if x alone stands for " white things," and y for " sheep," let xy stand for " white sheep ;" and then Chapter 2:11 In this and in all other respects the words " and" " or" are analogous with the sign + in algebra, and their laws are identical. ....Let x represent " white things," y, "sheep" and let + stand for " and" and " or".

What is the difference between xy representing white sheep and x+y which may represent white and sheep? Am I missing something?

Answer 1

$xy$ means things that are white and sheep, i.e. white sheep

$x+y$ means things that are either white or sheep. This includes white sheep, but also such things as white saladshooters, and black sheep.

Answer 2

$xy$ here is something that's both white and shep, while $x+y$ is something that is white, or is a sheep (or both).