For as the heavens are higher than the earth, so are My ways higher than your ways, and My thoughts than your thoughts. (ISAIAH 55:9)
A galaxy is a system that usually consists of billions of stars held together by gravity. We see them far away and near our own galaxy. Our galaxy is called the Milky Way. The nearest galaxy depends on how we define a galaxy. There are masses of stars much smaller than the Milky Way that are considered a galaxy. There are many of these, and the close ones are also considered satellites of our own Milky Way galaxy. Think of all the moons, which are satellites that surround Jupiter. The smaller masses of stars are satellites to the Milky Way just like those moons are satellites of Jupiter.
If we count these satellites of the Milky Way as galaxies, then the next closest galaxy is Canis Major Dwarf, which is about 25,000 light years away. Of course, astronomers still debate about the specifics and classification of these minor galaxies, including this one. There are about 19 satellite galaxies in the next major galaxy, called Andromeda Galaxy (M31). But it would be the closest galaxy that is about the size of the Milky Way (2.5 million light years across). In fact, it is a little larger than the Milky Way, and it shares the same spiral shape. Spiral galaxies are good examples of why the universe is not billions of years old. If they were, the spiral arms should have all been wound up already!