A typical blockchain is like a music box: the tune is soldered into the mechanism, and to change it you have to take the whole thing apart. If developers want to change the rules, they have to stage a fork, splitting the network into two branches. That's painful and expensive.
Enso works differently. Rather than baking logic into node code, it stores logic in the blockchain's state itself, as data. The state is made up of objects called actors. Each actor is a tiny program with its own address and memory. When a user sends a transaction, it becomes a message in a shared queue. The node pulls messages one by one and hands them to actors. Those actors can create new messages. This continues until the queue is empty.
Thanks to this, developers don't need forks for routine updates. Users see fewer network splits. The blockchain becomes like a computer fed by punch cards, not one with programs soldered onto the motherboard.
The name Enso refers to the Zen Buddhist circle drawn in a single brushstroke: simplicity and completeness in one gesture. The virtual machine also strives for minimalism: just two types of entities, actors and messages.