A value proposition explains why customers should choose your product over competitors. It answers what problem you solve and what unique benefits you deliver.
Uber's value proposition is 'Tap a button, get a ride' — simple transportation solution. Slack's value proposition is making team communication effortless. Each clearly communicates the core benefit.
A strong value proposition must be specific, measurable, and differentiated from competitors. It should be communicable in one sentence and resonate with your target audience's most important needs.