Guides
Terms
#### In-Process Database Management System {#docs:guides:glossary::in-process-database-management-system}  
The DBMS runs in the client application's process instead of running as a separate process, which is common in the traditional client–server setup. An alternative term is **embeddable** database management system. In general, the term _“embedded database management system”_ should be avoided, as it can be confused with DBMSs targeting _embedded systems_ (which run on e.g., microcontrollers).  
#### Replacement Scan {#docs:guides:glossary::replacement-scan}  
In DuckDB, replacement scans are used when a table name used by a query does not exist in the catalog. These scans can substitute another data source instead of the table. Using replacement scans allows DuckDB to, e.g., seamlessly read [Pandas DataFrames](#docs:guides:python:sql_on_pandas) or read input data from remote sources without explicitly invoking the functions that perform this (e.g., [reading Parquet files from https](#docs:guides:network_cloud_storage:http_import)). For details, see the [C API - Replacement Scans page](#docs:api:c:replacement_scans).  
#### Extension {#docs:guides:glossary::extension}  
DuckDB has a flexible extension mechanism that allows for dynamically loading extensions. These may extend DuckDB's functionality by providing support for additional file formats, introducing new types, and domain-specific functionality. For details, see the [Extensions page](#docs:extensions:overview).  
#### Platform {#docs:guides:glossary::platform}  
The platform is a combination of the operating system (e.g., Linux, macOS, Windows), system architecture (e.g., AMD64, ARM64), and, optionally, the compiler used (e.g., GCC4). Platforms are used to distributed DuckDB binaries and [extension packages](#docs:extensions:working_with_extensions::platforms).