From Wikipedia:
"Blue laws, also known as Sunday laws, are laws designed to restrict or ban some or all Sunday activities for religious or secular reasons, particularly to promote the observance of a day of worship or rest. Blue laws may also restrict shopping or ban sale of certain items on specific days, most often on Sundays in the western world. Blue laws are enforced in parts of the United States and Canada as well as some European countries, particularly in Austria, Germany, Switzerland, and Norway, keeping most stores closed on Sundays."
Specifically with respect to alcohol sales, every community can be a little different regarding Sunday sales. When I lived in Minnesota, for example, all proper liquor stores were shuttered completely on Sundays, and you could buy beer/wine only from grocery stores, but the selection was absurdly small.
Where I live now...on a Sunday, I can buy all manner of beer and wine from Kroger (big brand grocery store), and they have a decent selection of both, but I can't buy beer or wine from the mom & pop shop across the street. They're restricted because...wait for it...they don't sell as much beer and wine as Kroger, so they're not allowed to sell beer and wine on Sundays...unless it's past noon...or not, depending on what township/town/county you're in. But Kroger can sell it 24/7 no matter where they are, unless they're in a dry county...except that some dry counties will let some restaurants serve, there's just no walk-away sales...except Kroger...sometimes.
Liquor/spirits...never on Sunday...unless it's below a certain alcohol content percentage.
All that means is, depending on where you live, you better have your alcohol for the Sunday big game or the family cookout bought by Saturday, or you're going to be very thirsty come Sunday.