The game of aikido is about mental training along with physical training. So, the movements in it signify the same.
Nowadays, in different schools, different styles of aikido are practiced. Many other different practitioners are Kisshomaru Ueshiba, Koichi Tohei, Morihiro Saito, Steven Seagal, etc. However, people enjoy watching and practicing diverse styles of aikido.
Talking about the history of iaido, it was started in the middle of the 1500s. As per the available documents, Hayashizaki Jinsuke Shigenobu is considered the organizer of iaido. Since then, many koryu or schools have introduced the martial art form. Some of the schools still practice it today.
The game of sojutsu and the use of yari became highly popular after the Mongol invasion in the 13th century. In later days, the Japanese modified the tops of the spears as per their requirements. Some new styles are developed to make them compatible with on-foot games. And some are designed for fighting from horseback. Although it was practiced in nearly 450 schools in ancient days, it is rarely found in recent days. However, nowadays, it is practiced in several Japanese Bujutsu Ryu and Ninjutsu schools.