On what basis did you get an EAD? People working on H1b do not get EADs. Probably what happened is that you applied for Adjustment of Status (the process of getting permanent residency within the US), and you applied for an EAD on the basis of being an Adjustment of Status applicant. You are probably applying for permanent residency based on the employer petition you mentioned earlier that is in the EB2 category.
The EAD is for you to work for any employer(s) you want. The EAD has nothing to do with your current employer and you do not need an EAD to work for your current employer as you are working for them under H1b. You would only need an EAD to work for another employer.
Note that since you are applying for Adjustment of Status under an employer-based category, switching jobs during the process could affect the Adjustment of Status (which in turn affects the EAD which is based on your AOS). Specifically, if you switch jobs less than 180 days after the AOS is filed (and it is still pending), the previous employer's petition would no longer be valid and your pending AOS would be denied. But if you switch jobs more than 180 days after the AOS is filed (and it is still pending), and your new job is similar to the original job, your petition remains valid and your Adjustment of Status can continue to be adjudicated. You can work for the new job(s) with your EAD and not need them to sponsor you for H1b or something like that.