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

# Glossary

<ParamField path="Database">
  A single database that runs on a database instance.
</ParamField>

<ParamField path="Database instance">
  Database host machine, may contain multiple databases.
</ParamField>

<ParamField path="Logical replication">
  Replication at the level of operations; describes the operation, the arguments and data (e.g., an `UPDATE` is applied to row X setting column Y = Z).
</ParamField>

<ParamField path="Physical replication">
  Replication of the on-disk data structures after an operation has been applied.
</ParamField>

<ParamField path="Primary database (DB)">
  The customer's database within a database instance that is being replicated. The source of truth for data for all copies of that database.
</ParamField>

<ParamField path="Write-ahead log (WAL)">
  Log used by a database to log database operations. Used for recovery replay or replication.
</ParamField>