Many different technologies exist. The choice can be between Open source and mainstream commercial products or if you know how, write code yourself. But for most of us we will buy off the shelf. First you need an operating system which is the backbone of the computer/device. You could choose between open source (Linux) or Microsoft Windows on most computer hardware or Apple (On apple devices).
Once you have an operating system you can add apps such as office, accounting programs or other specific types depending on what you need. The list is huge. Each type of software usually comes with support from the vendor. Support can be enhanced by including a provider such as Databit IT to assist in installation, setup and configuration.