The authoritative source would be RFC7640 in which you will find the following definition:
Traffic scheduling: provides traffic classification within the
network device by directing packets to various types of queues and
applies a dispatching algorithm to assign the forwarding sequence
Traffic shaping: controls traffic by actively buffering and
smoothing the output rate in an attempt to adapt bursty traffic to
the configured limits.
So shapping is about controlling the bandwidth used while scheduling is about giving priority to some kind of traffic against others.
Note however that I never saw a device claiming to be "RFC7640 compliant" and you may well find implementation that doesn't strictly adhere to those definitions. There's often some mix and match in this area.
Actually this RFC status is:
This document is not an Internet Standards Track specification; it
is published for informational purposes.
and therefore nobody has any obligation to adhere to it.