Streaming (Roblox)

Streaming is a mechanic where the game is loaded to the client as it is required. Any PVInstances are loaded when within range, and their descendants follow suit. Anything without a position which is a child of workspace will be replicated immediately.

Positive effects

• Faster loading times. You'd not believe how much faster a game can load with StreamingEnabled
• Less latency. If the client is dealing with less replication, the data packets are smaller and more packets can be sent with less choke/loss (lag)
• Better device compatibility. The Streaming is designed to scale to the hardware capabilities of the device. If it's a slow device, less parts will be loaded in and the device will be able to handle the game far more easily.

Negative effects

• Unexpected behaviour. If you try to do anything on the client, you have to always assume that the Instance may not be there. That's a lot to compensate for in some cases.
• Events not firing. If a tree falls in a forest with nobody around, does it still make a sound? The question is the same for Roblox - Just because a sound should be able to be heard by a Player doesn't mean it will be; if the Part containing it is out of range and not streamed in, the sound will be too.
• Undefined behaviour. It's not exactly defined what happens to events on Instances that are streamed/in out, and what events they fire. You'll have to be careful of that.

I hope this was comprehensive.