Long story short: Bing is Microsoft’s old search engine plus some new features, rebranded and advertised aggressively to try and take search market share from Google.
No, it’s not some new Google-killer startup or a genius’s revolutionary breakthrough in search. It’s just Microsoft putting a new face on old products and distancing themselves from the branding to make it look new.
Before consolidating everything into Bing, Microsoft had two search engines and a bunch of web properties that searched for different things. They’ve now consolidated everything into one interface and renamed it Bing.