Voadam
Legend
2014 5e DMG page 11:Where does it say that?
Greater deities are beyond mortal understanding. They can't be summoned, and they are almost always removed from direct involvement in mortal affairs. On very rare occasions they manifest avatars similar to lesser deities, but slaying a greater god's avatar has no effect on the god itself.
Lesser deities are embodied somewhere in the planes. Some lesser deities live in the Material Plane, as does the unicorn-goddess Lurue of the Forgotten Realms and the titanic shark-god Sekolah revered by the sahuagin. Others live on the Outer Planes, as Lolth does in the Abyss. Such deities can be encountered by mortals.
Quasi-deities have a divine origin, but they don't hear or answer prayers, grant spells to clerics, or control aspects of mortal life. They are still immensely powerful beings, and in theory they could ascend to godhood if they amassed enough worshipers.
The whole divine rank sidebar in 14 is a weird "how it is in 5e D&D" thing in a section on Other Religious Systems for your campaign. It is inserted between mystery cults and monotheism. The Whole Gods of Your World section is set up to be all about DM choice of setups.
GODS OF YOUR WORLD
Appendix B of the Player's Handbook presents a number of pantheons (loose groupings of deities not united by a single doctrine or philosophy) for use in your game, including the gods of established D&D worlds and fantasy-historical pantheons. You can adopt one of these pantheons for your campaign, or pick and choose deities and ideas from them as you please. See "A Sample Pantheon" in this section for an example.
As far as the game's rules are concerned, it doesn't matter if your world has hundreds of deities or a church devoted to a single god. In rules terms, clerics choose domains, not deities, so your world can associate domains with deities in any way you choose.