No, the sun is actually pretty small compared to a lot of other stars. Have a look at this picture:
It shows how different things compare in size. The brightest star in the nights sky is Sirius, and in the picture you can see that it’s bigger than the sun, but you can also see that there are other stars that completely dwarf both Sirius and the sun!
That’s how big things would be if you put them next to each other though. Here on earth, the sun is the star that shines the most light on us, and it looks the biggest (but just because it’s so close).
It’s definity not the biggest, there are many that are much, much bigger, but it is the brightest. When we astronomers use the term ‘bright’ we mean in terms of how bright it looks to us which is determined by distance so in that sense the sun is the ‘brightest’. If we’re talking about things that are the same distance away then we use the term ‘luminosity’. In terms of Luminosity the sun is quite dim.