Tell me why Pluto is no longer a planet.
There are a few reasons:

1. In the early 2000s, astronomers began discovering other objects in the outer solar system that were similar in size to Pluto. These discoveries challenged the notion that Pluto was unique and highlighted the lack of a formal definition of what constitutes a planet.

2. In 2005, the IAU formed a committee to officially define what constitutes a planet. After much debate, they proposed a definition in 2006 that a planet must directly orbit the sun, be large enough to be nearly round in shape due to its gravity, and must have cleared the area of its orbit of other objects.

3. Pluto did not meet the third criterion, as its mass is much smaller than the other planets and its orbit is filled with many other objects in its size range (called the Kuiper Belt). So in a controversial vote, the IAU demoted Pluto from planet to dwarf planet status in 2006. The vote was controversial because it was a narrow majority and there was ongoing disagreement about the criteria.

4. However, the new definition is now widely accepted. Classifying Pluto as a dwarf planet recognizes that it is different from the other major planets in our solar system—it is much smaller, has an unusual elliptical orbit, and shares its orbital space with many other objects. So while it was an adjustment, the new classification is more scientifically accurate and helps clarify what officially constitutes a true dominant planet vs. other objects in the solar system.
Name some other dwarf planets and where they are
Dwarf Planets:

Pluto - It is located in the Kuiper Belt, beyond the orbit of Neptune
Eris - It is located in the scattered disk region beyond the orbit of Neptune
Haumea - It is located in the Kuiper Belt, beyond the orbit of Neptune
Makemake - It is located in the Kuiper Belt, beyond the orbit of Neptune
Ceres - It is located in the asteroid belt between Mars and Jupiter
Orcus - It is located in the Kuiper Belt, beyond the orbit of Neptune
Quaoar - It is located in the Kuiper Belt, beyond the orbit of Neptune
Sedna - It is located in the scattered disk region beyond the orbit of Neptune
Varuna - It is located in the Kuiper Belt, beyond the orbit of Neptune
2007 OR10 - It is located in the Kuiper Belt, beyond the orbit of Neptune
Salacia - It is located in the Kuiper Belt, beyond the orbit of Neptune

Dwarf Stars:

Proxima Centauri - It is located in the Alpha Centauri star system, which is 4.24 light years away from the Sun
Barnard's Star - It is located in the Ophiuchus constellation, approximately 5.96 light years away from the Sun
TRAPPIST-1 - It is located in the constellation Aquarius, approximately 40 light years away from the Sun
Wolf 359 - It is located in the Leo constellation, approximately 7.78 light years away from the Sun
Lalande 21185 - It is located in the Ursa Major constellation, approximately 8.29 light years away from the Sun
Sirius B - It is located in the Canis Major constellation, approximately 8.6 light years away from the Sun.