Who did Knights work for and what is a vow?
Knights fought for their lords who in turn fought for their king. The king might fight for his own kingdom, or help out another king or the Pope as a favour. Knights were not only used in battle, but also to guard a lord's lands and castle. The Middle Ages were very violent times, so there was a lot of fighting going on that lords needed help with.
A knight would typically give 40 days of service each year to the lord he was working for. He vowed or promised to be loyal to his lord and protect and serve him when needed.
The rest of the year, when he was not serving his lord in battle or on guard, the knight was expected to train his skills. Weapon practise included training with the two-handed sword (1), battle axe (2), mace (3), dagger (4), and lance (5). The image below shows these weapons; click on the image to enlarge.
The Medieval Knights could practice their knightly skills at tournaments. Various forms of combat were practised at the tournaments including jousting, archery, and hand to hand combat using swords and other weapons. The video below shows a jousting tournament, where knights battle on horseback with lances.