Eye hand coordination, speach, crawling, eating. The same surival things we dream about, just the ones they're working on.
Studies have shown we re-create our dailiy lives in our dreams with different scenarios to train in our sleep so when we encounter them while awake we already have possible actions and outcomes.
There was one big research project I watched that was pretty fascination where they REM deprived a group of students and conducted visual problem solving tests each day and the ones that were allowed REM sleep scored much higher.
They also wired up a lab rats brain and somehow coded it to 'show' what it was dreaming. During the day the rat ran a maze and the sensors shows what areas of the brain was active at each turn, during REM sleep the same centers activated and recreated the maze at night. The rat progresively ran the maze faster and faster when it was allowed REM sleep.
The theory is that millions of years ago mammals evolved with this 'training' technique to give us an edge in survival. It's why we dream about our fears, so when they really happen to us we already worked out possible reactions in our sleep and can better cope with the fear when things happen.
One common dream among military personal is in thier dreams thier weapons malfunction in different ways. I used to have a reoccuring dreams that the trigger on my gun wouldn't budge no matter how hard I pulled even with guys running right up to me, that's when I started looking into dreams to figure it out and found how common that scenario is among military/LEO. The theory again being because these professions rely on thier gun for survival that the dream is meant to prepare them for when thier gun fails them, and train them with alternate means to deal with a threat as well as remove or lessen the real fear if it really happens and allow a better reaction because it's already happend a ton of times in thier dreams.