Say you had the numbers 3 and 4. The LCM is the lowest number that both 3 and 4 will factor into.
The multiples of 4: 4,8,12,16,20,24
The multiples of 3: 3,6,9,12,15,18,21,24
They both factor into 12 and 24 but 12 is the least common multiple or smallest number they both go into :) I really hope this helps!! :)