The difference between defining and non-defining relative clauses

Hi

Please check me. I correctly understand . I try to understand this using example :

The athletes who failed the drug test were disqualified. (defining)
The athletes, who failed the drug test, were disqualified. (non-defining)

1)About defining. There are many athletes . And some of them who failed the drug test and were disqualified. And some of them were who not failed the drug test and not disqualified. We speak about athletes who were disqualified. But there are also other people.

2)About non-defining. Here we speak about all athletes. There are not others . Only athletes who failed the drug test and they were disqualified.

Do i understand corrently or not?

Thanks