Inclusive design

Inclusive design is a design process (not restricted to interfaces or technologies) in which a product, service or environment is optimized for a specific user with specific needs. Usually, this user is an extreme user, meaning that this user has specific needs that are sometimes overseen with other design processes. By focusing on the extreme users, Inclusive design will enable them to be able to use it, while many users having (temporary) similar needs will also be covered.
Inclusive design and universal design.
Both inclusive design and universal design have as a goal making a product, service, or environment more inclusive, meaning that a wider diversity of people can make (easy) use of it. Universal design is generally more focused on a single solution that can be used by as many people as possible, whereas inclusive design involves designing for a specific individual or use case, and extending this to others, as described in the Steps to inclusive design.
Universal design is mostly used in the built environment and product design to make sure that the building or product is accessible for all people of different abilities. Inclusive design can be applied to any product or service and intentionally does not group people together. Instead, inclusive design considers the full range of human diversity with respect to ability, language, culture, gender, age, and other forms of human difference and how to serve the diverse individuals that will be using the product or service.
Inclusive design and accessibility.
Inclusive design and accessibility are often grouped together since they are each focused on making products or services available to a wider range of people. However, accessibility is more limited in scope compared to inclusive design. 
Accessibility is focused on specific accommodations for disabilities (whether in a digital or physical space) or other areas of access that directly prevent accessing an experience. 
Inclusive design describes a process of welcoming all people from different and intersectional backgrounds to use your products and services in ways that are meaningful to them, while including diverse individuals throughout the research and design process.
Accessibility is one piece of inclusive design, but it doesn't take into account many of the areas that inclusive design does (culture, identity, different perspectives) or involve considerations around work processes and planning. 
In general, designs created through an inclusive design process should be accessible by nature, as people with different abilities are considered as part of the design process. But accessible designs aren't necessarily inclusive if they don't move beyond accommodating people of different abilities to also take into account sociocultural and intersectional aspects of individuals.
Steps to inclusive design.
Here are steps that are typical to inclusive design: 