microvms as espoused by things like firecracker offer full machines but have tradeoffs like no gpu (which makes it boot faster)

hyperlight shaves way more off - (eg: no access to various devices that you'd find via qemu or firecracker) it does make use of virtualization but it doesn't try to have a full blown machine so it's better for things like embedding simple functions - I actually think it's an interesting concept but it is very different than what firecracker is doing