They're not the same thing.
A "marker" is an older term that (usually) non-geneticists use to refer to what the rest of us usually refer to as SNPs or indels or some other feature of the genome (even a mutation) that is (usually) associated with risk for a condition/disease or causative of the disease. This term in the genetics context is probably confusing, since it doesn't separate coincidental associations from biologically important genomic features. It's an overly descriptive term.
A "biomarker" is usually meant as some physiologic value that helps either with early diagnosis or prognosis -- for example, we speak of "biomarkers" for Alzheimer's disease or cancer as something we can measure in the patient that may provide a clue as to what is happening early in the disease process. Biomarkers are therefore regarded as important early discriminators of disease severity, and could be used to guide therapy.
"Marker" chromosomes, of course, are something completely different...
The question could have provided a little more detail and context -- but nevertheless, welcome to the site.
Sounds like the same thing to me. What would be the context of your question?
You've had a couple of awkwardly worded and unclear questions just in the last couple of hours, perhaps it would be a good idea to read this informative article, written by some of the contributors here, about how to maximize the resources of the BioStar community.