hacker in residence can do a bunch of things. build new website for them, build stuff on portfolio companys APIs, start building their own project. depends on the vc and what they want. Also depends on the hacker and what they want.
entrepreneur in residence is supposed to be working on a startup- while also participating on investments- they can bring in deals, help portfolio companies, vet imminent investments, etc.
I'm the Hacker-in-Residence at Quotidian Ventures, an early-stage venture firm in New York. My background is in server-side engineering in data science.
Ataub24 explained it well, though it varies widely from firm to firm. In my case, I spend a significant chunk of my time working with the partners and the rest of the venture team on managing the investment portfolio and helping with dealflow. When there are opportunities to use technology or data to improve our workflow and decision-making process, this can come in handy, though that's not always the case. A lot of this is similar to what an EIR might be responsible for doing as well, though with a technical bent.
The rest of the time can be thought of as "20% time", except without a specific % attached to it. While there's the possibility of building a project that could be spun out, this isn't an explicit goal or requirement; my value-add comes from my ability to assist with dealflow and the rest of the work on the venture side, so the rest of my time doesn't come with any obligation, so to speak. In this way, it's not too dissimilar from a traditional 'artist-in-residence'. (This is where Quotidian differs from a number of other firms).
entrepreneur in residence is supposed to be working on a startup- while also participating on investments- they can bring in deals, help portfolio companies, vet imminent investments, etc.
helpful?