> ## Documentation Index
> Fetch the complete documentation index at: https://docs.flagsync.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Key Concepts

> Learn the essentials to kick off your feature management journey.

## FlagSync Basics

Master the building blocks of feature control:

<CardGroup cols={1}>
  <Card title="Feature Flags" icon="flag" href="/flags/overview">
    A feature flag toggles features on or off without redeploying code.
    <Card>Hide `beta-feature` until ready, then enable for testing.</Card>
  </Card>

  <Card title="User Segments" icon="users" href="/flags/targeting-and-rollouts#user-segments">
    Group users by attributes (e.g., location, role) to target flags or experiments.
    <Card>Show `beta-feature` to premium users in Boston.</Card>
  </Card>

  <Card title="Percentage Rollouts" icon="percent" href="/flags/targeting-and-rollouts#percentage-rollouts">
    Release features gradually to a fraction of users for safe testing.
    <Card>Enable `beta-feature` for 10% of users, scale up if stable.</Card>
  </Card>
</CardGroup>

## Data and Insights

Understand how to measure your features:

<CardGroup cols={1}>
  <Card title="Impressions" icon="eye" href="/impressions/overview">
    Record flag evaluations automatically when `flag()` is called.
    <Card>`flag('beta-feature')` logs if a user saw `Enabled`.</Card>
  </Card>

  <Card title="Events" icon="bolt" href="/events/overview">
    Track user actions (e.g., clicks) via the SDK’s `track()` function.
    <Card>Log a `purchase_event` to measure `beta-feature`’s impact.</Card>
  </Card>

  <Card title="Metrics" icon="chart-line" href="/metrics/overview">
    Measure flag impact (e.g., conversion rates) using events and impressions.
    <Card>Track `beta-feature`’s click-through rate for engagement.</Card>
  </Card>

  <Card title="Experiments" icon="flask" href="/experiments/overview">
    Compare feature variations to measure impact via metrics.
    <Card>Test two `beta-feature` designs and pick the winner by clicks.</Card>
  </Card>
</CardGroup>

## How FlagSync Works

FlagSync’s components work together to launch and optimize features—like a new checkout flow—with data-driven confidence:

<Steps>
  <Step title="Flags control what’s live (e.g., `New Feature`)" />

  <Step title="Segments decide who sees it (e.g., premium users)" />

  <Step title="Rollouts pace the release (e.g., 25% at a time)" />

  <Step title="Events and Impressions capture data (e.g., clicks, views)" />

  <Step title="Metrics reveal the impact (e.g., higher engagement)" />

  <Step title="Experiments test variations (e.g., A/B designs)" />
</Steps>

<Check>
  FlagSync lets you roll out, measure, and optimize features in one seamless flow.
</Check>

## Next Steps

* Set up a flag in [Quickstart: Create a Flag](/quickstarts/flag).
* Explore [Experiments](/experiments/overview).