My DS is 20 months. I think he is advanced in some ways, and behind in others. I think thats pretty normal
His physical abilities, balance, and motor control are pretty great I think. He is a dancing MACHINE. Spins, jumps, hops, thows his arms about, its madness when he decides to dance! He's been doing it for quite some time, I forget exactly how long though. He was running at 11 months. He insists on going up and down stairs by himself, and he doesnt scoot, he walks, using the handrail. He freaks out if I try to help, he's been doing this for a few months. We bought him a tricycle with a parent push bar, but it took him about 10 min of it to figure out how to do the pedals. He climbs EVERYTHING. I've got some blankets laid out next to our couch now, because his favorite thing is to run across the room, leap up onto the couch, and then vault over the ends or the back. He is really good at putting things together, like board puzzles, and lacing toys. Most of his toys are around a 3+ yr level He loves taking things apart, and figuring out how to put it back exactly the same way. He is really aware of how or where things 'go'. If I have his toys laid out a certain way on his shelves, he'll put them back in that exact same order later in the day.
I am pretty sure he is behind verbaly though, He only consistently says 'Mom' and 'Dad'. The thing that he actually says the most, is 'HUH?!' All day, its 'Huh? HUH? Mom mom mom huh?' He has said a few other words, but he only says them once, or twice maybe, and then we never hear them again. One time he said banana, really clearly, three times in one day. And he's never said it since! I dont forsee him speaking anytime soon. He is pretty creative about communicating non-verbally. He does not recognize any shapes, colors, numbers or letters, even though we do read to him quite a bit, and we have toys/books with numbers and alphabet. But he does know the names of other things, like his toys.
Like, for instance, he has a block puzzle of the alphabet. He cannot identify any of the colors or the letters if I ask him (even though we go over them), but if I say 'lets do your alphabet puzzle' he goes and gets it off of his shelf, and he can put it together.
His big thing right now is his lacing blocks. He understands 'lets play with your lacing blocks' (gets it off the shelf) or 'lets put the lacing blocks away'. (puts the blocks back into the box, and back on his shelf) He likes to sort them into piles of similar shapes, but he cannot identify 'blue' or 'round' etc, out of them. He just looks really confused when we try to label things by color or shape for him.
I do worry about his speech sometimes lately.
Edit to add: He is pretty good at naming body parts. He can point out : Hair, ears, eyes, nose, mouth, tongue, shoulder, elbow, hand, fingers, belly, belly button, bum, knees, feet, and toes. And he can point out other peoples too. Like, 'where are Dads knees?'.