In English Common Law, a contract resulted from the figurative "meeting of the minds" between two individuals or firms. Typically this agreement would be codified in writing, a handshake or some other mode of expression. Once an agreement is reached it becomes the focal point from the Common Law's perspective. That vision of the world will serve to inform other legal mechanisms like determining whether a "breach" of contract has occurred or assessing "damages".
One interesting item to note is that the legal system in the United States has developed quite a sophisticated judicial apparatus to deal with contracts gone awry. The modern legal adjudication of contracts is largely ex-post. And expensive to boot. Smart contracts (best understood as self-executing agreements instantiated in computer protocols) allow the performance of credible transactions without third parties. Judiciaries play a valuable role in modern society, but they are, alas, categorical middle-men providing the service of ex-post dispute resolution.
An interesting theme I will be observing is how much effort goes into developing thoughtful agreements or smart contracts before the transaction occurs. It stands to reason that more legal hours should be put towards developing solid smart contracts at the beginning since an ex-ante clean-up by a judiciary is almost guaranteed to be messy.
At least one case study seems to prove this theory wrong in practice. The modern form of raising funds through token offerings. "Just send some ether to my personal address and I will send you some token that I made that may not be worth anything" seems to be a process (and now industry standard) that lacks anything in the way of forethought. Individuals seem less concerned with drafting the Platonic ideal for a "meeting of the minds" than with raising money quickly. I take the opposite view and wonder what an ex-ante corollary to a judiciary would look like...
I look forward to the "fine code print".