daf bit: Yevamot 102

(Today's daf is 103.)

If a man refuses to perform levirate marriage, there is a ritual called chalitzah that involves taking off one of his shoes. The talmud here discusses what constitutes a "shoe", and among things, the mishna says that chalitzah performed with a sock is invalid. The g'mara explains that this teaches that a sock is not a shoe, and then discusses different kinds of socks, including a type that has pads that make it pleasurable to walk around in. This leads to a discussion of Yom Kippur, on which it is forbidden to wear shoes. What counts here? Do pleasurable padded socks count, on a day when we are to afflict ourselves? The g'mara repeats a teaching that no man may walk about in slippers in his house, but in socks he is permitted -- "slippers" refers to leather slippers, and "socks" to felt. So, socks made of cloth are socks, but socks made of leather are shoes. (102b)

(The halahca is that leather shoes are forbidden on Yom Kippur, which is why you sometimes see people wearing Nikes or Crocs. I use Chinese slippers, which have cloth uppers and plastic soles. And no, walking around on plastic soles isn't particularly comfortable.)