Integration is: incorporation into society or an organisation of individuals of different groups. Which is the case when organisations create a dedicated group to address minorities, e.g. women dedicated groups, etc.
Inclusion means that a person with a disability, women, whoever, has the same rights, access and choices as everyone else in a community.
When we create a dedicated group, even if our intentions are good, we somehow further segregate them, making them a special category, marginalising and labelling. It creates further separation rather than inclusion and it instils in others who are not part of that group also the feeling of exclusion. "There is no way to inclusion. Inclusion is the way". This means having everybody sitting at the same table as equals; it means acceptance and respect. It means we pay attention to how we treat and make feel people rather than how many of X, Y, Z we have in a group. It further means we value and measure the impact our actions have on humankind as whole.
We can include something in to something which may be defined as inclusion. Any included things can be excluded at anytime. Integration is nothing but, being part and partial of something which is supplimentary and complimentary to the ingredients of the combination.
My viewpoint is inclusion is to be a part of the school in all school activities with appropriate modifications and adaptions. The inclusion does not mean that you are a part of the school through bureaucracy (i.e. it happens in Greek education, parallel support programme or Resource room). The term inclusion focuses on every person, such as a disabled person, a person with different sexual orientation, an immigrant person, etc. It focuses on the person as a whole personality.
On the other hand, integration is to integrate a person in a school activity with other students for a specific time. It focuses on a separate system. Why? Because his/her diagnosis requires more participation in school activities by the side of socialisation and normalisation.
In conclusion, what do I mean with this? I mean that inclusion is by the side of the social model of disability and the integration is by the side of the medical model. Some scholars and supporters of the social model of disability support this viewpoint.
From my point of view integration is to ensure that people with needs are incorporated into educational environments based on them, however, the inclusion starts from the concept of providing education for all, it is the institution that must adapt to the individual and accommodate the spaces, schedules and look for the necessary aid to achieve quality in the education of all the children who attend it.
Integration is more of a social process that is concerned with providing services and opportunities by the authorities (it could be the government, CSOs, or even schools) while inclusion also has a personal and interpersonal relationship factor involved. To include someone would mean to go out of the way to bring them into a process, and that process could be integration itself.
The confusion could be because the term inclusion is commonly used by even people who are not conversant with special needs education so it is easier to use the term inclusion even when one meant integration