Also, if it is a right, who is to provide it?
The fact that there's nobody to provide it, doesn't mean that it's not a basic human right.
[0] https://www.un.org/en/about-us/universal-declaration-of-huma...
The declaration on human rights is not really government-centric, so the US-style free speech comparison makes little sense.
> what do they really mean?
They're a yardstick to measure how well we as humanity, and, more specifically particular regions or systems, measure up to what we, as humanity, consider to be the things that every human should (expect to) have. (Sorry for the bombasity.)
For instance, if we lived in a libertarian/anarchist utopia, with no government, it would still make sense to ask whether people's human rights were being met.
The UDHR is an aspirational document that has no legal force in and of itself.
Look at the debate around making Internet access a right: https://en.wikipedia.org/wiki/Right_to_Internet_access
Same debate around free healthcare et al, which last time I checked somebody had to provide.