Tin Can API is what the SCORM standard is evolving into.
SCORM is a standard that allows elearning content and assessments to integrate with an LMS and be shared across multiple systems.
The problem with SCORM is that it only allows certain types of learning and assessment to be recorded.
Typically, a SCORM-compliant course or module will have multimedia content about a subject followed by some interactive activities like drag and drop activities or quizzes. But this isn’t the only way people learn.
Learning happens through a range of different online and offline activities. For example, people can learn through their interactions on social media, by building something in real life, or by reading a book. In short, people learn things by experiencing the world and life in general.
This is why Tin Can API is also sometimes called xAPI (because the x stands for ‘experience’). It enables a person's experiences to be counted towards their learning and assessment.
"Tin Can API is an elearning standard that makes it possible to collect data about the wide range of experiences a person has (online and offline)."
So, in summary, SCORM allows elearning multimedia content to be uploaded into an LMS, and records data about the student’s interactions and results into the LMS. Tin Can API allows a lot more types of data to be stored.
More more information see Rustici Software's Tin Can / xAPI overview.