You can change a lot of stuff on each image. Be aware, every gene changes the overall coloring/ pallete a bit. Is a bit like getting your shower warm enough: every change goes overboard and you have a few trials being scalded or frozen before you get it right. Same here. Good for laughs though.
The bottom line is this page is great to fine tune a portrait but big changes are best obtained with compose, upload or crossbreed. Paid Subscribers also have a powerful tool they can use here, they can Use Custom Genes created by Artbreeder users.
chaos: A higher value (above 1) will make the face different, less "real" with elf years and crazy colors. Play with makeup, art, chaos and you can get some very crazy faces
age: Adds crows feet, white hair, aging the face fast: each .1 is about 10 years. Negative values make the portrait younger
gender: a negative value will make hair longer and features more feminine. The hair effect is faster than the facial features so going up/ down 0.1 to 0.3 is a great way to give your portrait a haircut or longer hair
width, height: A positive value zooms into the face, making it dominate the 520 x 520 square
yaw, pitch: rotates face left to right (yaw) or up and down (pitch)
asian, indian, black, white, middle eastern, latino hispanic: Adds racial features to the face, a positive "asian" value will make eyes almond shaped and skin color trending towards Japanese / Chinese people's skin color. This setting alters coloring / pallete a lot
art: This setting introduces "unreal" colors and make the portrait look more like a painting / art, less like a photo
red, green, blue: Tints the entire pallete of the portrait. Pretty useless for realistic photos but great for artistic ones
hue, saturation: Tints the entire pallete of the portrait, but this one is useful to get realistic photos color corrected, i.e. black and white pictures can gain a bit of color. Great for artistic portraits
brightness, sharpness: Can improve badly lit uploaded photos or soften / sharpen portraits.
happy, angry: Those affect the eyes and mouth mostly, making the portrait "frown" or smile.
blue eyes: Changes the entire pallete with focus on the eyes. Too much here will make a black haired portrait blonde. For green eyes, use the negative values
earrings: Doesn't do much on low values. Ideal for copying a portrait: Go to "Edit genes", add 0.1 earrings, save. It will be almost identical
yaw: rotates the face to make it look left or right, very slowly. Ideal for copying a portrait: Go to "Edit genes", add 0.1 yaw, save. It will be almost identical
pitch: rotates the face to make it look up or down, very slowly Ideal for copying a portrait: Go to "Edit genes", add 0.1 pitch, save. It will be almost identical
eyes open, mouth open: As the name says, this will make the face have wider openings for eyes, or close them, same for mouth. For mouth play also with "happy" and "angry" to get the facial expression you want
eyeglasses, hat: Will add glasses or a hat to the face
black hair, blonde hair, brown hair: Changes the entire pallete not just the hair. To get "ginger" / red haired" people play with brown hair from a blonde or black haired base.
facial hair: Will add beard to the portrait but also make features less feminine. If you want a bearded lady you best try with crossbreed, here will be hard!!
makeup: adds lipstick and eye shadow and such, slowly