What problem does Polkadot solve?

Could you please elaborate on the problem that Polkadot aims to address? It seems to be a hot topic in the cryptocurrency and finance world, but I'm still a bit hazy on its specific challenges it's trying to overcome. Is it about scalability? Interoperability between different blockchains? Or is it something else entirely? I'm curious to know how Polkadot proposes to solve this problem and why it's considered a significant breakthrough in the field. Could you provide a concise yet informative description of the issue and Polkadot's solution?