Anumber cube is rolled many times with the results shown in the table below.
number rolled 1 2 3 4 5 6
number of rolls 13 12 12 14 11 18

the theoretical and experiment probabilities for rolling a 2 are [close together, the same, not close together].

The experimental probability is the number of two rolled divided by the total number of rolls...

12/(13+12+12+14+11+18)

12/80

3/20  (15%)

The theoretical is simply the number of twos on the die divided by the total number of numbers on the die...

There is 1 two and 6 total numbers so:

1/6  (16 2/3 %)

No one specified what the definition of "close" is, but I would say a 1 2/3 percent difference is significant if you are going to have many trials

100(3/20-1/6)/(1/6)

600(9-10)/60=-10%  

So the experimental probability will wind up predicting 10% less occurrences than the theoretical probability would.  That can be quite a difference for a large number of trials.  The larger the sample the closer you get to the theoretical probability.