What is the meaning of "service bits" in Bitcoin?

// Note that of those who support the service prefix, most only support a subset of
// possible options.
// It's fine at run time, because we're going to use them as a onehot if they do not support the
// bits of service we want, but we should update them to support all the bits of service wanted by all
// release as soon as possible to avoid it as much as possible.

Reference: https://github.com/bitcoin/bitcoin/blob/master/src/chainparams.cpp#L116