Scaling up/Vertical Scaling and Scaling Out/Horizontal Scaling. These terms are used often in the Cloud referring to the flexible way of increasing the performance and computing.
Scaling Up or Vertical scaling means to increase the memory, storage or compute power on an existing virtual machine. For example, you can add additional memory to a database server to make it run faster.
Scaling Out or Horizontal scaling means to add extra virtual machines to power your application. You may create many virtual machines configured together and use a Load-Balancer to distribute work across them.