What's important to realize is that this vocabulary is NOT codified across the industry. So what different people mean when they use these terms is… different. I will explain these terms in what I think is the most accepted version.
Chest Voice: Lower pitches where the vocal folds are shorter and fatter. Chest voice falls below Eb4. The thyroid-arytenoid muscle is very dominant. Example: The beginning "Rah rah ah ah ah" of Lady Gaga's Bad Romance. If you try to use pure chest voice too high, it might feel like yelling and gets VERY tiring.
Head Voice: Higher pitches where the vocal folds are longer and thinner. Lighter contact between the folds when they vibrate. The cricothyroid muscle and ligament are dominant. Falls above an Eb4. Example: Chappell Roan's “Good luck, babe. Well, good luck babe” in Good Luck Babe.
Falsetto: This is a gendered term to refer to a “weaker” head voice in male singers. High notes do not need to be weak. Check out… so much of Freddie Mercury's material. Falsetto is rad and important in contemporary music. Nothing false about it.
Mix: Basically anything in between. A strengthened, brightish head voice or lightened chest voice. It's a huge spectrum. Think about long vocal folds that aren't too thin - or shorter vocal folds that aren't too thick. A lot of researchers say that mix is not a register, but rather a timbre - but practically, most folks refer to it as a register.
Getting into the weeds more:
Head Dominant Mix: Vocal folds that are more similar to head voice but have more closure and strength. Example: Adele “eeeeeeeee" (of the word easy) in Easy on Me.
50/50 Mix: Right is that neutral place between head and chest dominant. This is so subjective - I think Sara Bareillis is often in this mode like in “keeping me down” in Gravity.
Chest Dominant Mix: Vocal folds are more similar to chest voice, but thinner/lighter than pure chest. Example: “I want your love and I want your revenge” in Lady Gaga's Bad Romance.
Belting: A usually used to describe very strong and powerful sounding mixes.
Screlting: Usually used to describe VERY high notes that we are giving the bright illusion of a belt.
True Belt: The beefiest of the chest dominant mixes.