Do you know what a lane means? It's like a place on the road that cars can drive in. So, a wide outside lane means a lane on the road that's extra big and wider than other lanes. This is done to provide extra space for cars, especially for those which are bigger or have something attached to them, like a trailer.
Sometimes, people also call it a "shared lane" because it's not just for cars, but also for people who are riding bikes. That means, both cars and bikes can use this wide outside lane to travel on the road.
The wider outside lane makes it easier and safer for bikes because they are given more space to ride. It also makes it easier for drivers because they can pass bikers more easily and without any danger of hitting them.
So, next time you see a wide outside lane on the road, remember that it's a special lane that both cars and bicycles can share together and that it helps everybody stay safe while they're travelling.