Library technical services is a term used to describe, in general, the processing and maintenance of a library's physical collection.
According to the textbook Introduction to Technical Services (7th ed), by Evans, Intner, and Weihs, the traditional technical services are:

• Identification: locating potentially worthwhile items to add to the collection
• Selection: deciding which of the identified items to add to the collection
• Acquisitions
  Library acquisitions
  Library acquisitions is the department of a library responsible for the selection and purchase of materials or resources for the library. Acquisitions may select vendors, negotiate consortium pricing, arrange for standing orders, and/or select individual titles or resources .-Functions:*Ordering,...
  
  : securing the items for the collection
• Organization: indexing and cataloging the items acquired in a manner that will aid the end-user in locating materials in the collection
• Preparation: labeling and otherwise making the items ready for storage in a manner that allows for easy retrieval

Technical services may also include:
maintenance of online catalogs

Library catalog

A library catalog is a register of all bibliographic items found in a library or group of libraries, such as a network of libraries at several locations...

, creation and maintenance of MARC records in the catalog, labeling, covering, security processing, and/or distribution of materials, maintaining a library's technology resources, such as servers

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

, OPAC

OPAC

An Online Public Access Catalog is an online database of materials held by a library or group of libraries...

s, circulation

Library circulation

Library circulation or library lending comprises the activities around the lending of library books and other material to users of a lending library. A circulation or lending department is one of the key departments of a library....

, scanners

Image scanner

In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop scanner where the document is placed on a glass...

, and other devices.