Island groups are a collection of multiple islands located in close proximity to each other. They can be found in various parts of the world and are formed due to geographical factors such as tectonic activity, volcanic eruptions, or erosion.

The British Isles, the Balearic Islands of the Mediterranean, and those of the Aegean Sea are all examples of island groups. These island groups share certain characteristics that make them fall into this category.

1. British Isles:
The British Isles is an archipelago located off the northwestern coast of mainland Europe. It is composed of two main islands, Great Britain and Ireland, along with numerous smaller islands. Some of the notable islands in the British Isles include the Isle of Man, the Channel Islands, and the Hebrides. These islands are closely situated to one another and are considered an island group.

2. Balearic Islands:
The Balearic Islands are an archipelago in the western Mediterranean Sea, off the eastern coast of Spain. This island group consists of four main islands - Mallorca, Menorca, Ibiza, and Formentera - along with several smaller islets. The Balearic Islands are well-known for their beautiful beaches, vibrant nightlife, and rich cultural heritage.

3. Aegean Islands:
The Aegean Islands are a vast group of islands located in the Aegean Sea, between the eastern Mediterranean Sea and mainland Greece. This island group includes popular destinations such as Crete, Rhodes, Santorini, Mykonos, and many others. The Aegean Islands are famous for their stunning landscapes, ancient ruins, and picturesque villages.

These island groups are classified as such due to their close proximity to one another and their geographical connection. They often share similar geological features, cultural influences, and historical significance. Island groups like the British Isles, the Balearic Islands, and the Aegean Islands attract tourists from around the world for their natural beauty, cultural heritage, and recreational opportunities.

In conclusion, the British Isles, the Balearic Islands of the Mediterranean, and those of the Aegean Sea are all examples of island groups. They consist of multiple islands situated close to each other and share common characteristics in terms of geography, culture, and history.