Service Mesh is a design to provide an infrastructure as a service layer within the cloud service. Sidecar is one example of such implementation.
SideCar as its name is acting as a decoupled component attached to other microservices to cater to those cross-cutting concerns. One example is a volume mount across microservices.
As mentioned in my other post, mount S3 as share drive, it’s a great feature to be able to access the S3 for CRUD operations. Some common use would embed the volume mount into each container or pod whichever needs the S3 access.