What are the dimensions

Just as it says in the product details, it 19 x 19 x 19 when open and standing. It folds down to about 2.5"-3" deep when folded. The table seems very sturdy when opened. I own plastic versions of this same product and was never really satisfied with them. I much prefer the wooden version. Just remember it is bare wood and a spray can on polyurethane might be good idea to help it last a long time. I know this is more info than you asked for but these were the same questions I had before I bought 2 tables, very happy with the purchase.

Can you use it as a chair? Can you sit on it?

I wouldn’t recommend it but haven’t or will I try to. Works nicely between my Adirondack chairs

Greetings! Does this collapse if you try to pick it up to move it with a glass, etc. on it? Thanking you in advance! Eileen

Yes, it does collapse if you pick it up with however, once it is in position, it is super sturdy. I wouldn't recommend trying to move its position with a glass on it however, I do highly recommend this product. It's made of wood and looks perfect on our dock.