How do VC get their money?

I'm curious, how do venture capitalists, or VCs, typically secure their funds? Are there specific sources they rely on, or is it a mix of different channels? Do they primarily target individual investors, institutions, or both? And once they've raised these funds, what kind of criteria do they use to determine which startups or projects to invest in? Understanding the funding process for VCs is crucial for entrepreneurs seeking investment, so I'd appreciate a detailed breakdown of how it works.