local t = {"a", "b", "c", "d", "e"}
print(table.find(t, "d")) -- 4
print(table.find(t, "z")) -- nil, because z is not in the table
print(table.find(t, "b", 3)) -- nil, because b appears before index 3
table.find(t, element) finds the index position of element. It returns nil if there is no element in the table.
t = table
element = thing you're trying to find
Its uses are
Quick verification that an element is in the table
Get the index of the element, probably so you can pop it from the list or any other index-based operations rather than element based