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

# Introduction

LedgerUp lets engineering teams measure usage over the API so finance teams can interpret it and create flexible contracts. Measurement resources track quantities over service periods. Billing resources define how that usage becomes revenue.

| Concept              | Description                                                                                                                                                             |
| -------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Customer             | A customer in LedgerUp. A customer can have multiple usage accounts.                                                                                                    |
| Account              | An account that owns grants and usage. You can link it to a LedgerUp billing customer and retrieve aggregated usage for a date range.                                   |
| Metric               | A company-wide definition of measured usage within a namespace. Usage events reference these shared metrics.                                                            |
| Grant                | An amount allocated to an account for a service period. A grant can expire.                                                                                             |
| Refill configuration | Automatic balance refill settings for an account and metric. When active, the minimum balance is the refill threshold and the target balance is the balance to restore. |
| Usage event          | A quantity of usage for an account and metric over a service period, such as phone-call minutes, credits, or seats.                                                     |
| Contract             | A customer's billing agreement. Rate cards and prices determine the final contract-line amounts.                                                                        |