They call that the “License to Depart”. Some traditions tell you to command them to leave. I don’t do that because I want them to bring their energies and forces into my life.
A banishing ritual clears the area you banish of all energies and entities. The purpose is to get back to a clean slate.
In other words, if I’ve just done a baneful ritual, I don’t want that same energy carrying over into my ritual to find my soulmate.
Here’s a link to one of the more powerful banishing rituals I’ve used:
Solar Banishing Ritual
And I don’t banish after an evocation because I don’t want to clear my space of those energies. I want them hanging around, building, and growing until I’m done with that purpose.
Besides, calling a spirit over to your house to hang out and then yelling at them to “get the hell out of my house” is just rude. 