ActiveX Data Objects (ADO) are a collection of COM-based objects developed by Microsoft to facilitate access to databases across various programming languages and platforms. ADO provides a unified interface for working with databases, allowing developers to execute SQL statements, read and write data, and manage transactions.

The main components of ADO include:

1. Connection: Establishes a connection to the data source and manages connection properties.
2. Command: Allows the execution of SQL statements or stored procedures on the data source.
3. Recordset: Contains a result set from a query or stored procedure and enables traversing and editing of records.
4. Record: Represents a single record in a recordset.
5. Field: Represents a single field in a record and allows access to its value.

ADO has often been used in the development of Windows applications, especially in conjunction with the Visual Basic programming language. It provides an efficient way to access and manage databases without developers having to worry about the specific details of database connection.