What is actually happening during a loading screen?
Far more than reading a file. A loading screen covers a sequence of expensive operations that must complete before a frame can be drawn — and modern games have largely become very good at hiding them rather than eliminating them.
What is actually being done:
Reading from storage, the obvious part, and frequently no longer the bottleneck.
Decompression. Game data is heavily compressed to reduce install size and read time, and must be expanded — historically a CPU-bound step, which is why faster drives alone did not shorten load times as much as expected. Modern consoles include dedicated decompression hardware precisely for this.
Shader compilation, translating graphics code for your specific GPU and driver. Consoles precompile; PCs frequently cannot, which is why PC games show "compiling shaders" screens and why skipping it causes stutter later.
Uploading assets to GPU memory, over a bus with finite bandwidth.
Constructing the world in memory — instantiating objects, building navigation and physics structures, spatial partitioning, and running level scripts.
Audio banks and streaming setup.
Connecting and synchronising in multiplayer, where the slowest player gates everyone.
How games hide it:
Streaming. Open worlds load continuously as you move, keeping nearby areas resident and discarding distant ones — which is why they rarely have loading screens after the first.
Corridors, lifts, crawl spaces and slow door animations, which are loading screens wearing a costume.
Cutscenes and unskippable logos, covering the wait.
Fast travel confirmations and inventory screens.
Why loads got longer before getting shorter. Asset sizes grew faster than drive speeds for years. Solid-state storage, hardware decompression and APIs that let the GPU pull data more directly have reversed the trend substantially.
Why a second load of the same level is faster — the operating system's file cache still holds the data in memory.
The loading tips exist because early testing showed players tolerate a wait better when given something to read.