The king divides his land into fiefs or estates and gives it (with everything on it included) to the local landlords. They are responsible for their estate.
The landlords grant some land to their vassal in return for 40 days of military service, certain payments, advice and loyalty pledged by their vassal. The landlord should also protect his vassal.
You have to help me first
A vassal could have more than one lord to whom he pledges loyalty. But to avoid conflicts, he often pledges his first loyalty to his liege lord.
No, I am your lord so you have to help me first
Feudal lords constantly battled battled for power so the castles were built to withstand attacks. This meant that the only way to gain land was to starve the defenders to surrendering to them.
Training to become knights was started from childhood (from the age of 7 yrs to 21 yrs). They were taught riding and fighting. This training was very cruel and was meant only for boys.
Women suprvised vassals, managed household, agricultural and medical tasks defended and even estate. Although they played an active role to support the society, they did not have the right to inherit property. The only exception is that when her husband dies, then she can get the property.