The choir of a church is the area reserved for singers and clergy; sometimes it is also called a chancel. The choir is usually located in the east end of the church, between the main altar and the apse. It is separated from the nave so that the members of the clergy could remain separate from the rest of the congregation.

This is Notre Dame de Paris, the chief cathedral and one of the most famous landmarks in Paris, France. Notre Dame was the seat of the Archbishops of Paris.

Beginning in the twelfth century in Europe, Gothic architecture dominated the building of churches across the continent, with its massive facades, extreme buliding heights, and ornate stone work. This style was used both in new churches like Rouen Cathedral and Lincoln Cathedral, and also in the rebuilding and renovation of structures, as with both Westminster Abbey and Notre Dame Cathedral. This was not the only church style, however, as the Greek churches developed their own massive church architectural style, exemplified by the Hagia Sofia in Constantinople (present day Istanbul).

This is the Florence Cathedral, a Catholic entity. This can been seen in a number of ways. The dome is particularly telling, as is the facade, which features a rose window. Both of these things are characteristics of catholic churches, which were being built in grander and grander style at the height of the gothic and Renaissance movements. Take special note of how the church looms over the neighboring buildings; at the time of its building, the Catholic church was the strongest entity in the land, and the buildings reflected that. 

Notre Dame has many of the typical features of Gothic cathedrals and differs from Romanesque cathedrals, which lack the height, light, and pointed arches of the Gothic style.

"Medieval" and "Religious" are too vague to be considered styles of architecture, and the Baroque period came centuries after construction on Notre Dame began. 

Although he was also a prolific writer and historian, Abbot Suger is arguably most famous for his contribution to the reconstruction of Saint-Denis in the middle of the twelfth century. With its adoption of new architectural styles and forms (the church has the first known example of a large "rose window" above the West portal, for instance), Saint-Denis is often cited as the first example of Gothic architecture and the cathedral that inspired the construction of countless others in France in the years to follow.

Although there are other French churches or cathedrals in this list of answers, the only one that is part of the Gothic architectural movement is the Notre Dame. In fact, the only answer, French or otherwise, on this list that is truly a Gothic cathedral is the Notre Dame cathedral.

This cathedral, known as the Reims Cathedral, was built in France in the year 1211.  It very accurately depicts the popular architectural trends that were popular in that time period, which is now known as the Gothic period. This period took place between the 12th and 16th centuries. Features popular in Gothic architecture that can also be seen on this cathedral are:

1) Vertical length over horizontal length.  Gothic buildings tended to be slender and tall.

2) Pointed arches

3) Spires and towers, especially when they come in doubles.

4) Ornate façades

5) Rose windows

Image citation: Photo taken by bodoklecksel (2006) https://upload.wikimedia.org/wikipedia/commons/e/e1/Reims_Kathedrale.jpg

The Chartres Cathedral of the early 13th century is an example of Gothic architecture. Its Gothic features are the following:

1) Vertical length over horizontal length.  Gothic buildings tended to be slender and tall.

2) Pointed arches

3) Spires and towers

4) Ornate façade (though not as ornate or decorated as other Gothic buildings)

5) Rose window

6) Groups of large windows

Image citation: Photograph taken by Tony Hisgett, accessed through Wikipedia Commons. https://commons.wikimedia.org/wiki/File:Chartres_Cathedral.jpg