DevOps is two things:
Applying the methods of modern software development (version control, automation, DSLs...) to operations (provisioning, config, deployment, monitoring, backups...).
Reducing silo barriers between devs and ops groups so that everyone is working together as a team, rather than blaming each other for poor communication and the resulting messes.
Then there are all the DevOps hijacking attempts, such as equating it to Agile or Scrum or XP, or insisting that it's a way to stop paying for expensive operations experts by making devs do it, or a way to stop paying for expensive devs by making ops do it, or a way to stop paying for expensive hardware by paying Amazon/Google/$CLOUD to do it.
No matter what your software-as-a-service company actually does, it will need to execute certain things:
have computers to run software
have computers to develop software
have computers to run infrastructure support
You can outsource various aspects of these things to different degrees. Anywhere you need computers, you have a choice of buying computers (and figuring out where to put them and how to run them and maintain them), or leasing computers (just a financing distinction), or renting existing computers (dedicated machines at a datacenter) or renting time on someone else's infrastructure. If you rent time, you can do so via virtual machines (which pretend to be whole servers) or containers (which pretend to be application deployments) or "serverless", which is actually a small auto-scaled container.
Docker is a management scheme for containers. VMWare provides management schemes for virtual machines. Kubernetes is an extensive management scheme for virtual machines or containers.
A continuous integration tool is, essentially, a program that notes that you have committed changes to your version control system and tries to build the resulting program. A continuous deployment system takes the CI's program and tries to put it into production (or, if you're sensible, into a QA deployment first).