Good sides together

When I refer to good sides together that can refer to either cutting or sewing:

Cutting with good sides together

A pocket is marked on the bad side of a piece of double-folded denim, ready to be cut good sides together. After cutting both layers, this will yield two pockets that are mirror images of each other.

Cutting with good sides together is a technique that is used when two identical, or mirrored pieces need to be cut.

When a pattern asks to cut a piece with good sides together, fold your fabric double with the good side/right side of the fabric to the inside, and the bad side/wrong side outside.

Now mark the pattern piece on the bad side of the fabric, and cut both layers in one go.

This gives you two pieces that are mirror images of each other.

NOTE
What if there is not obvious good side?

When cutting out something without an obvious good side (like interfacing), what matters is that you cut two mirrored pieces, rather than two identical ones.

Sewing with good sides together

A piece of denim is sewn with good sides together.

Sewing with good sides together is the standard approach to making a seam.

By placing the good sides of the fabric together, both pieces will be joined with the seam allowance to the inside of the garment. This is what’s done for the vast majority of seams.

When there’s no specific instructions on how to construct a seam, it’s good sides together.

Fabric grainHemming