Shukuba is like a place where horses (and sometimes people too) could take a rest during a long journey a long time ago. It was kind of like a hotel, but not as fancy, and it was mostly just for travelers who needed a break. People who were traveling on important business or important government stuff or just people that wanted to visit their family would stop at shukuba to rest, eat and change their horse. Think of it like a pit stop during a car race, but for horses and people!