system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can toddlers remember how to walk,"talk", know certain words but when we get older we can only start remembering things as young as 4?
gpt
The type of memory that babies to do quite well is referred to as "semantic memory".  This allows them to know their parents, recognize the foods they like and don't like, remember to not do something that they learned sucked when they did it the first 10 times and so on.

What they lack is referred to as "episodic memory". The best theories we have currently tell us that we lack the ability to pull together distinct memories into a coherent rememberable "episode".  E.G. the experience we have in the visual context isn't bundled with the auditory, the emotions, and then also isn't anchored around other memories and episodes.  Basically, we have a shit ton of input, but no scaffolding on which to place it.

Most believe that the pulling together of this requires the development of the hippocampus beyond where it in an infant - it supplies the contextual glue and scaffolding to form what an adult thinks of as "memory".  That said, the hippocampus may not be developed, but also may not have enough stuff in it yet on which to have found patterns and meaning.  Until you are 2-4 it isn't physically developed enough, and it hasn't had enough raw material run through it to develop patterns and coherency.