There are many different types of integrated curriculum:
Connected - This is when topics surrounding disciplines are connected which allows students to review and re-conceptualize ideas within a discipline. However, it has its shortcomings because the content focus still remains in one discipline.
Sequenced - This is when similar ideas are taught together although in different subjects which facilitates learning across content areas, but requires a lot of communication among teachers of different disciplines.
Shared - This is when teachers use their planning to create a integrated unit among two disciplines.However, this method of integration requires a lot of communication and collaboration between the two teachers.
For example, a social studies teacher and a science teacher can decide to plan a unit in which the students will be completing a research paper on the Civil War. The social studies teacher can use this as an opportunity to teach about the Civil War and it's causes and effects as well as how we gather information using first and second hand sources, while the English teacher can use this as an opportunity to teach proper MLA format when citing a paper, how to format a research paper, as well as grammar, spelling, and other writing techniques.
Webbed - This is when a teacher decides to base all subjects areas around a central theme which motivates students to see the connection to the theme within the different subjects.