Many toddlers are passionate little people. Being caught in the transition between baby and child means that they can be both hard work and delightful in the space of a few minutes.
Two-year-olds tend to approach problems head-on in all areas of their lives - working round something, or being flexible, is just not an option. They are not being unreasonable, they are just incapable of reason - quite a different thing all together.
Toddlers are usually egocentric - unable to see anyone else's point of view or feelings - which can make life tough for everyone concerned. Although they will start to play with other children at this stage, he or she won't be mature enough to understand that they have feelings too. They may snatch toys, hit and bite other children, cause a commotion, and even enjoy doing so!
Your toddler will probably watch other children at play, and may even join in for a few minutes. But playing with others requires a degree of co-operation and an ability to plan ahead that they just doesn't have. He or she will quickly revert to their solitary game where they can control what's happening, taking with them some of the ideas from the other children's games. Each time one toddler does something different, the other toddlers are likely to try it too.
Sharing is a hard lesson to learn. Just occasionally your toddler will accept the need to take turns - a first step on the way to real sharing.