How can i return the differences between 2 tables?

[CoderLogan (Logan)]

So if a player equips a pet and i have the old table of equipped pets and the new table of equipped pets how would i return only the differences between both those tables of equipped pets?

[12312ababc]

for i, v in pairs(firsttable) do
	for a, b in pairs(secondtable) do
		if v == b then
			table.insert(thridtable, v)
			table.insert(thirdtable, b)
		end
	end
end

for i, v in pairs(thirdtable) do
	for a, b in pairs(firsttable) do
		for c, d in pairs(secondtable) do
			if v ~= b and v ~= d then
				table.insert(fourthtable, b)
				table.insert(fourthtable, d)
			end
		end
	end
end

the fourth table should have the difference. and the third table should have the pets that are the same