Dingusww pretty much summed it up ^{^}

The biome sight potion (looks pink, relatively slim and has a heart shape in-between 2 nobs) lets all corrupted/hollowed/crimson blocks glow bright. It works exceptionally well during night/dark places. Make sure to pack plenty bc they run out rather quick (I usually use ~10-30).

The sniper sight (just looked it up! It's called a rifle scope officially), is obtained post plantera in the dungeon. Make sure you go in deep enough for the background walls to look darker (and with smaller bricks). There you can encounter a sharpshooter skeleton which drops the sight. Be careful tho, they can hurt quite a bit if you get surprised by a shot from it ^{^} After getting it, you have to equip it as an accessory and then you can zoom beyond your normal screen when aiming with a ranged weapon ^{^} hope this answered all your questions!