What's the difference between codons and DNA triplets?

So basically, they are the same thing but just one is for DNA and one is for mRNA.

Thank you so much!

Yep! Just a reminder though that the DNA triplet and mRNA codon are complimentary to each other, so their codes are not the same, but basically opposites. E.g. if the DNA triplet is ACG, the mRNA codon would be UGC (U because RNA has uracil instead of thymine).
And there are also anti-codons which are the tRNA version (they are also complimentary to the mRNA codon so are identical to the DNA triplet except where the DNA triplets have T, the tRNA anti-codons have U)