At their most basic level, Kubernetes [1] and Mesos [2] both use a client/server type architecture, where you install a client on many compute nodes, then the server part farms out jobs (in the form of containers) to these client compute nodes. Mesos does not do scheduling, and is pretty low-level in terms of interfaces, so you would typically run some type of software which talks to it via API, like Marathon [3], Aurora [4], or Hadoop [5]. Then Marathon/Aurora/Hadoop/etc tells Mesos to farm out compute jobs to these end client nodes (aka schedules). Complexity can quickly go up depending on your hosting environment, scale, and HA requirements. There is actually a really good high-level overview diagram of what a mesos/hadoop/zookeeper setup looks like here [6].

The stack looks something like this for Kubernetes/Mesos (top down):

  - Kubernetes and Mesos (client/server packages depending on node type)
  - Docker (container engine)
  - OS (Ubuntu/RHEL/etc)

What are some use-cases?

  - you have more work than can fit into one server
  - need to distribute load across N+ nodes
  - Google heavily uses containers (not k8s, but that inspired these patterns)
    - Gmail/Search/etc all run in containers [7]
  - Apple, Twitter, and Airbnb are running Mesos today [8, 9]

There are a bunch of revolving services, like:

  - distributed key/values stores (etcd/zookeeper)
  - load balancers
  - image registries
  - user interfaces
  - cli tools
  - logging/monitoring/alerting
  - etc

But, to answer your question, the main difference between Kubernetes and Mesos, is that Kubernetes offers an opinionated workflow, built-in scheduler, and patterns for how containers are deployed into this cluster of compute notes. The pattern is baked in from the start via Pods, Labels, Services, and Replication Controllers. It also helps to know that Kubernetes comes from Google, where they have been running containers in-house, so much of this workflow (pods, services, replication controllers, etc), comes from their internal use-cases. That's the 10,000 foot view.

[1] https://github.com/GoogleCloudPlatform/kubernetes

[2] http://mesos.apache.org/

[3] https://mesosphere.github.io/marathon/

[4] http://aurora.apache.org/

[5] https://hadoop.apache.org/

[6] http://mesos.apache.org/assets/img/documentation/architectur...

[7] http://www.wired.com/2013/03/google-borg-twitter-mesos/

[8] http://www.infoq.com/news/2015/05/mesos-powers-apple-siri

[9] https://www.youtube.com/watch?v=E4lxX6epM_U