Under normal circumstances, your income is taxed where you actually work, regardless of where the company is located. So if you were telecommuting from NY to MA, you would be treated as a NY-based employee. All your income would be NY income. Your employer would have to withhold NY tax, and not MA tax. Your W-2 would not show any MA income. You would file only a NY tax return, not MA.
What makes the current circumstances not normal is that MA adopted some temporary regulations regarding telecommuting during the Covid-19 pandemic. I'm not familiar with the details. Someone else might post some information about it, but I suggest that you consult a local tax professional, preferably in MA, who can tell you whether and how the temporary regulations affect you.
Also note that we have been talking about working exclusively in NY. If you occasionally work in the company's office in MA, even for a short time, the money you earn for working in MA is MA income, and is subject to MA tax. Then you are back to filing two state tax returns, as I described above.
