Most currencies have value because we trust the governments who issue them (at least enough to still be in power and not drastically mess up any more than they already are). Bitcoin gets its value from the trust people have in the network (which is pretty impressive) and the fact that the currency is deflationary over time because there is a limit to how much bitcoin will ever exist.

That’s the easy way to look at it I think. Of course you are free to dig into the technical aspects!