They both mean "of", typically it would be spelled more like "land o' lakes", but they removed the apostrophe probably for marketing reasons. As for the other questions, butter comes in both salted and unsalted, but salted is more commonly bought. Likely because it tastes better on toasted bread/bagels/etc. You'd get unsalted for baking and recipes so you can properly measure the salt. The pack comes with four sticks, not one huge block (though that is rarely available). The sticks are four ounces each, so 1/4 of a pound. Its makes a lot more sense in Freedom Units rather than sane metric units. The sticks have measurement lines on the paper wrapper so you can just cut off a needed amount.
For more butter facts... well actually no don't refer others to me hah
The W11 installer sadly doesn't allow that anymore with the current versions. If you have that older installer, keep it safely archived.