What comes in technical documentation?

The answer is in respect to the IT/Software Development.
There are several documents; we can state them under “Technical Documentation”.
It depends on the methodology used in Program / Project.
If we take an example of SDLC, Technical Documentation can be categorized under the Deliverables.
There are five major phases we can look into for common programs / projects:1.
Envisioning Phase - Kick-off Presentation - Business Requirements Document (BRD) - Program Architecture Document (PAD) - Program/Project Management Plan (PMP) - Requirements Traceability Matrix (RTM) - Phase Exit Review Presentation (PERP) - Peer Review Form - Status Report - Program Schedule2.
Planning Phase - Infrastructure Requirements Documentation (IRD) - System Requirements Specification (SRS) - Test Specification Document (TSD) - Release Plan (RP) - Change Request Form / Change Request Log3.
Developing Phase - Technical Design Specification (TDS) - Data Classification Document (DCD) - Testing Criteria Assessment - Test Cases / Use Cases - Source Code Scripts (SCS) - Test Cases & Results - Unit Test and Development Integration Test Cases - Implementation and Back-out Instructions4.
Stabilizing Phase - Business Sign-Off Proofs - Test Results Log - User Training Guides5.
Deploying Phase - Lessons Learned Workbook - Go No-Go for Production Release - Project Closeout Document

Technical documentation is generic term covering different types of documents.
Unlike user's guides and other end-user documentation, technical documents are more system-oriented.
These include software documentation such as design/architecture documents, deployment guides, use cases, and so forth.