I don't understand the guiding stuff lol ╥﹏╥

So basically the Sentinels (sometimes referred to as Espers) are people who have awakened with powers and they use their powers to fight in dungeons or just supernatural monsters (think your basic dungeon leveling manhwa). The twins are sentinels to be aware.

Then guides are people who have also awakened but they have a different power, to guide the sentinels. Because sentinels have a drawback that if they use their powers too much without guiding then they can like go manic or become weakened. The MC is a guide.

Hope this helps

Basically sentinels are the DPS and espers are healers. (In games sense)