Is 24 a factor or multiple of 36

Neither. A factor is when a number fits in to another number. For example, 6, 2, 12 and 1 are all factors of 12. A multiple again is when a number fits into a number but in a different way (2,4,6,8,10,12,14... are all multiples or 2)
24 and 36 both have common factors (12) which means that 12 is a factor of both of those numbers.

"Factors" always divide into the number without a remainder,
so they're all smaller than the number.

"Multiples" are what you get when you multiply the number
by another one, so they're all bigger than the number.

Now, even though  24  is smaller than 36, that doesn't automatically
mean it's a factor of 36.  You have to check it out, and make sure
it can go into  36  evenly, without a remainder.

(36) divided by (24)  =  1 and 1/2 . 

                                or  1 remainder 12 .

Ooops !

1,  2,  3,  4,  6,  and  12  are all factors of BOTH  24  and  36 .

But  24  is not a factor of  36 .