Less than is the symbol that you see here in red < that we use to compare numbers that are not equal when the smaller number is written first.
Less than means the same thing as smaller than.
Therefore, you can use less than or smaller than to show that the number on the left is less than or smaller than the number on the right.
6 < 15 Read as six is less than fifteen
1/5 < 1/2 Read as one fifth is less than half
-9 < -2 Read as negative nine is less than negative two