1/3 is a repeating number and 3/10 is 3 divided by 10.
1) Because those two numbers when divided generate those quotients:

1/3 is an irrational number a repeating one also represented as 3/9 while 3/10 is three divided by 10.
2) So, 1/3 is a repeating number and 3/10 is 3 divided by 10.