These cutting instructions are just for the default Brian block. Adjust your cutting accordingly if you have/are making changes to the block.
If you do not have someone to help pin you into Brian then you may find it easier to Cut 2 Front parts with seam allowance and sew the backs up when constructing so you can pin in the front.
A block is a basic shape on which other patterns are based. They are sometimes also called slopers, although purists will argue that a block and a sloper are different things.
Blocks are typically not made as-is but rather serve as a basis for other patterns.