Here's why:

* Cylindrical projections imagine the globe wrapped in a cylinder.

* The meridians (lines of longitude) are projected onto the cylinder as straight lines, hence they are "straightened out".

* The parallels (lines of latitude) are also projected onto the cylinder, but they are not always straight.

There are various types of cylindrical projections, each with its own strengths and weaknesses:

* Mercator projection is the most famous, used in many maps. It preserves angles, making it good for navigation but distorting areas near the poles.

* Transverse Mercator projection is often used for maps of smaller regions and can minimize distortion in the area of interest.

* Gall-Peters projection is an equal-area projection that shows continents in their true relative sizes, but distorts shapes.

Let me know if you'd like to learn more about specific cylindrical projections!