All three measure what your room does to the sound. They differ in how deep they go, what they cost, and how much work they ask of you.
The closest thing to a pro app on iPhone. It plays a sine sweep and hands you PEQ values to type into your receiver or streamer. Basic measurement is a free download; the room-correction features unlock with a paid Tuning Bundle. Best if you just want parametric EQ out of a phone.
Also on iPhone, but it goes from measurement to a plain-language plan: where to move speakers, what treatment to add, what EQ to set. It exports REW, FIR, PEQ, miniDSP and CamillaDSP, and takes a UMIK-1/2 when you want lab-grade accuracy. Free.
The free desktop reference. Room EQ Wizard is the deepest, most flexible tool there is — but you need a laptop, a calibrated USB mic like the $80 miniDSP UMIK-1, and an evening to learn it. Best if you want maximum control for $0.
Want it to just work on your iPhone and tell you what to do — Acouvero. Want raw PEQ numbers to enter yourself — HouseCurve. Want pro-grade depth for free and you enjoy the tooling — REW. They are not really competitors: most people start with the phone and only open REW when they want to go further.