Placing a different square between pieced squares is referred to as an alternate set.
In this quilt, the light pink squares alternate with the patchwork blocks. The pink squares are an alternate set. This quilt is also an example of a diagonal set as the blocks are turned on point (diamond-like instead of squares).
In the small wall hanging below there are 4 blocks cut from floral fabric. They alternate between the red/tan patchwork blocks. This another example of an alternate set.
After quilters make their quilt blocks, they need to decide on a quilt setting. There is no right or wrong setting. It is up to the quilter to decide what is most pleasing. Learn about different ways to set your blocks in your quilt in Quilt Settings.