If you opt for active monitors, they usually feature jack, XLR, phono, digital and/or USB connections, which are designed to be hooked straight into your audio interface or computer. If your interface has balanced outputs, opt for your monitors’ balanced XLR or jack input to reduce unwanted noise.
When working with passive monitors, you’ll need to send your interface or computer output to a separate external amplifier and then connect that to your monitors. At the very least, active monitors also include a level control, while room-compensating EQ controls are also common.