Memory encoding
Memory encoding is the first step of memory, where your brain turns what you see or hear into a form it can store. The stronger you encode something, by adding meaning or pictures to it, the easier it is to recall later.
Encoding happens the moment you take in new information. Your brain doesn't save things exactly as they come in. It changes them into a kind of code it can keep. This is why two people in the same lecture remember different things.
How you encode matters a lot. If you just hear a word once, the trace is weak. If you connect it to something you already know, picture it, or say why it matters, the memory is much stronger. That deeper kind is often called semantic encoding.
Most weak memory isn't a storage problem. It's an encoding problem. The information never went in clearly in the first place, so there's nothing solid to pull back out later.
Sofia keeps forgetting a list of dates for history. So she ties each one to a quick image and a short story in her head. The dates stick, because she gave her brain something to hold onto instead of bare numbers.