Ciliates are a diverse group of single-celled eukaryotes that are characterized by having cilia, which are short, hair-like projections that beat rhythmically to propel the organism through water or to move food particles towards the cell.

Key characteristics of ciliates:

* Cilia: Short, hair-like projections that beat rhythmically.

* Two nuclei: A larger macronucleus and a smaller micronucleus.

* Complex internal structure: Includes specialized organelles for feeding, digestion, and excretion.

* Wide range of habitats: Found in freshwater, saltwater, and even soil.

Examples of ciliates:

* Paramecium: One of the most well-known ciliates, often used in biology classrooms.

* Stentor: Large, trumpet-shaped ciliates that are often found in freshwater ponds.

* Vorticella: Ciliates that attach to surfaces and have a contractile stalk.

Note: While ciliates are the most prominent group with hair-like projections on their flagella, there are other organisms, such as some flagellated protists, that have similar structures. However, these projections are typically referred to as flagella rather than cilia, and they are longer and fewer in number.