Hi,
I spy quilts are quilts made for children as entertainment. They are usually a one patch design which is a collection of different novelty prints. The idea is for the child to try and find how many differnt print blocks in the quilt. Kind of like the traveling in the car game where the passengers look for things along the way. They are often made of 8 sided pieces but plain squares or triangles would also work. They can have a holiday theme like Christmas or Halloween or be gender specific.
Flip and fold is a way to both assemble a top and quilt it as you go. It requires either precutting all of the pieces of the top, back and batting before sewing or at least precutting the top pieces. Depending on the intended use of the quilt and the type of batting used it can be fast and pretty simple or very complicated.
A rag quilt is basically the same method as the flip and fold. You precut squares of top, back and batting usually in flannel or homespun. You then sandwhich each block and sew it to the next block to make rows. You keep all of the seam allowances on one side of the quilt. When the top is big enough to suit your purpose you carefully clip all of the raw edges of the seams like you would when easing in a sleeve or other curved piecing. YOu then put the whole quilt throw a rough laundry cycle and hot dryer. The result is a raggedy edged quilt on one side and smooth seams on the other. It is also usually very heavy.