text: You must mean universe, not galaxy.\n\nWe live on planet Earth,  which is in a solar system. A solar system consists of a star (we call ours the sun),  planets which orbit the star, and maybe other debris and gases. Solar systems are in galaxies. Our galaxy is the Milky Way. It's a barred spiral galaxy and it's a big one. Our galaxy is 100,000 light years across. That means, traveling at the speed of light, it'd take you 100,000 years to get from one side to the other if you went straight across the disk.\n\nOutside of the galaxy is mainly empty space (heck, galaxies have trillions of stars and massive clouds of dust and gases and most of it is still mainly empty space). There may be rogue stars or junk that got flug out of a galaxy here and there but they're generally few.\n\nDoes the universe have a boundary? Probably,  but the nature of it probably isn't anything we'd be familiar with...not like a wall or anything. Can we ever get there? No, we are well within the universe and even if we could travel the speed of light and live forever, it's thought the universe is expanding at an accelerating rate so we'd still never get to the edge, and if by change we mysteriously appeared at the edge and move along with it, there may be some physical process which would prevent us from realizing it.