Commonly abbreviated UX, is a ubiquitous term in Human-Computer Interaction (HCI), and is:

What is User Experience?

"A person's perceptions and responses that result from the use or anticipated use of a product, system or service"

The field of UX focuses on maximising 5 aspects:

What's UX Purposes?

Delight

Satisfaction

Motivation

Efficiency

Productiveness

Marsh, J. (2016). UX for Beginners: 100 Short Lessons to Get You Started. Sebastopol, United States: O'Reilly Media, Inc.

Psychology
Usability
Design
Copywriting
Analysis

has 5 component disciplines:

UX

Travis, D., & Hodgson, P. (2019). Think Like a UX Researcher. London, United Kingdom: CRC Press.

UX

Tasks

User Research
Usability Evaluation
Prototyping
Interaction Design
Visual Design
Information Architecture
Technical Writing
UX Leadership

Different UX roles simply take charge of different subsets of these UX tasks.
Teo Yu Siang and the Interaction Design Foundation. Copyright terms and license: CC BY-NC-SA 3.0

UX Roles Exist to Serve the Design Process

Empathize
Define
Ideate
Prototype
Test
User Interview
Contextual Inquiry
User Observation
Data Analysis
Information Synthesis
Brainstorming
Worst Possible Idea
Dot Voting
Paper Prototyping
Wireframing
Hi-fi Prototyping
Usability Test
User Test
Heuristic Evaluation
UX Designers Take Charge of All 5 Phases of the Design Process
UX Designer
Product Roadmap
+
Product Design
Made on
Tilda